5 ms·

What is copyleft?

52 points by gexos 10y ago

chungy 10y ago
> I prefer to think of the distinction in this way: permissive licenses provide the maximum freedom for downstream developers (including the ability to use the open source code in a closed source project), whereas copyleft licenses provide the maximum freedom for downstream users. This is a common analogy but it never sits well with me. Really, the permissive licenses allow the code to show up in places that copyleft licenses would not allow it. There are a ton of open source projects used in Microsoft Windows or iOS thanks to their permissive licensing -- and neither Microsoft nor Apple are legally obliged to give anything back. Copyleft licenses prevent the software from being forked into a proprietary program and the changes hidden from the user. To take a random example, if Microsoft took GNU gzip and included it with Windows, and then extended it with new features, Microsoft would be obliged to provide the source code to those changes. If they took OpenBSD's implementation instead, they wouldn't be obliged in the same way (though they still _could_). Remaining entirely in the open source world, these licenses concern redistribution of software. A user on OpenBSD does not feel they have any less freedom than a user on GNU/Linux. They don't have any less freedom, after all. Users on both systems retain the full gamut of freedom. To run for any purpose, to study the source code, to modify the source code, to redistribute the software verbatim or modified. The difference shows up when it comes to this: Do you want to be an asshole? OpenBSD permits the option -- you can distribute a fork without the source code. You cannot do that with a GPL-licensed system. The FSF and other GPL advocates usually ride on the premise that opening up the possibility for downstreams to be assholes is bad, with few exceptions. I do respect their opinions, but I feel like the history of open source (and the *BSDs, even) show that such assholes don't get very far. They simply cannot compete with the pace of open and transparent development and die off on their own. Frankly, being an asshole is an irrational and unprofitable (socially and commercially) move, and trying to nanny the behavior away isn't all that necessary.
- Flimm 10y ago
  You're comparing users of OpenBSD to users of GNU/Linux, but why not compare both of them to users of Windows and OS X? Why is FLOSS software pitted against each other, instead of FLOSS software against proprietary and closed source software?
  - chungy 10y ago
    I'm sorry, I didn't mean to pit them against each other, just pointing out that users of either system enjoy the same freedoms regardless of the license choices. :-) Windows, OS X, iOS, and all other proprietary systems do, in fact, restrict users and objectively have fewer freedoms than free ones.
    - AimHere 10y ago
      And there is, or was, BSD code in both Windows and OSX, some of which was locked off in proprietary parts. OSX also contains some GPLed code, all of which is available to the user under righteous free software terms (as is at least some of their permissive-licensed code). The problem that Stallman and the FSF complain about isn't the relative freedom of the users of OpenBSD and GNU/Linux, but what happens to the freedoms of users who are further downstream.
- vertex-four 10y ago
  There's not a small number of cases where people's work was coopted to create successful proprietary software. JunOS is closed-source and based on FreeBSD - the PS4's OS similarly so. When I went scrolling through an old iPod's copyright page, there's an incredible amount of MIT/BSD-licensed software in there. And so on and so forth.
- JackdawX 10y ago
  > Really, the permissive licenses allow the code to show up in places that copyleft licenses would not allow it. There are a ton of open source projects used in Microsoft Windows or iOS thanks to their permissive licensing -- and neither Microsoft nor Apple are legally obliged to give anything back. This whole sentence is backwards isn't it? A libre license does not restrict code from being used by Microsoft or Apple, it is those companies that restrict their developers from using libre licensed code. The license doesn't care who uses it. Apple used the GCC project as their primary compiler for many years, contributing objective-c to it.
- ent 10y ago
  Copyleft licenses are more about the freedom of users in the future, instead of now. If all software was mit/bsd licensed, there wouldn't be any need for gpl as anyone could modify and redistribute any piece of software freely. Gpl is intended to force us toward that state in the future.
- cyphar 10y ago
  > I feel like the history of open source (and the BSDs, even) show that such assholes don't get very far. Some versions of the SONY PlayStations are based on FreeBSD. The users of said PlayStations don't have any software freedom because the entire OS is proprietary. Assholes like this do exist, and if FreeBSD (and the other BSDs) were copylefted this wouldn't have happened. There are other examples (essentially any example of a company using BSD as the basis for their OS), but the point is pretty clear IMO.
bkuhn 10y ago
Those who wish to learn more about copyleft after reading Ben's article may also want to look at the copyleft guide https://copyleft.org/guide https://copyleft.org/guide for more information. Ben is a contributor to the copyleft guide, so we'll likely merge in his article into the Guide.
dhimes 10y ago
Can you make money writing and selling copyleft-licensed software? The licenses always appeared to me to make that difficult. I write one, sell it, and the purchaser can now give it away for free. But I probably just don't understand it.
- cyphar 10y ago
  The same argument is true for any free software. If you sell free software, then the purchaser necessarily must have the freedom to distribute said software. So copyleft hasn't changed anything in that regard. And there are several companies that sell free (and even copylefted) software. SUSE and RedHat are the prime examples -- the way it works is that you sell support licenses. So if they want to get L3 support for a bug they found (or want you to work on a new feature) they have to pay you. It's a fairly simple model (though more complicated than the standard proprietary model of "my binaries are holy and you must pay me for them" -- which I always found to make no sense because software isn't a real thing).
  - dhimes 10y ago
    I was really asking a question, but I think I understand your answer. I can see where there is a business case for it, but also the other. As an example from another field, my architect drew up plans for my house. I'm only allowed to use those plans for that house. I can't build another house just like it, and I can't sell the plans to somebody else. His expertise and hard work went into making the plans. It's no more "real" than a print-out of a program. Yet it would be very hard for him to make a living if other architects could just take his plans and use them. And the idea of selling giving the program away for free but charging to fix the errors may not be the best for all cases. I can see the case for copyleft, but I don't think it's the only case. (Not that you said it was- in fact, I've heard some people say something like that but not too many.)
    - cyphar 10y ago
      > I can't build another house just like it, and I can't sell the plans to somebody else. That wouldn't be considered "free software" if house designs were the same as software. But they aren't -- software serves a functional purpose and is something you use constantly throughout your life. House plans are essentially used once to build your house and that's about it. Though of course you could argue that an architect could have a business model that allows for their clients to resell the plans (by selling customisations to plans or creating new plans for each customer). > Yet it would be very hard for him to make a living if other architects could just take his plans and use them. It would also be hard for "users" of the plans to be able to ask for another architect's opinion on the plans. Or to say "this architect is not doing as I say, I will take these plans to someone else who can help me better". > And the idea of selling giving the program away for free but charging to fix the errors may not be the best for all cases. You can also sell improvements or features. In fact, you can get contract work with people paying you to implement features in $freeSoftwareProject. Sure, it's not a very common model but it does exist. > but I don't think it's the only case. It's not the only case, but as a developer it's the case I always aim for. Licensing something under a lax license is generally a tactical move (it would be a greater benefit if this wasn't copylefted), but I personally will always opt for copyleft because then I can guarantee that the eventual users of my software will have freedom.
anjbe 10y ago
Discussions of copyleft versus permissive licensing always seem to cover the same “freedom for users versus freedom for developers” clichés and the same tired slavery metaphors. My dislike of copyleft is emphatically not because I want to enable proprietary software. I hate proprietary software, and don’t use it on my machines. No, my biggest complaint about copyleft has always been that it prevents other free software from being able to use it. Copyleft licenses actively lead to incompatibility. Remember when LibreDWG, an AutoCAD file parser, couldn’t be used in various free software CAD projects, because LibreDWG is GPLv3+ and FreeCAD, etc were GPLv2 only? http://libregraphicsworld.org/blog/entry/libredwg-drama-the-end-or-the-new-beginning http://libregraphicsworld.org/blog/entry/libredwg-drama-the-... If FreeCAD had been under a permissive license, it would have been able to link against LibreDWG. If LibreDWG had been under a permissive license, FreeCAD would have been able to link against it. If they were both under a permissive license, they would have been able to be linked together and share code directly! How about when NYC released open building and address data? A laudable move, one that helped several open source projects, the largest probably being OpenStreetMap. OpenStreetMap is under a copyleft license, and though they benefit from NYC’s data, due to the licensing NYC can’t make use of OpenStreetMap’s improvements without a convoluted parallel construction scheme: https://www.openstreetmap.org/user/lxbarth/diary/23588 https://www.openstreetmap.org/user/lxbarth/diary/23588 A common response is that the onus is on NYC to release their data under a copyleft license so they can benefit. But there are often significant (even legislative!) barriers to doing that, especially in the United States where government entities are often required to release data to the public domain. How about changing that legislation? Well, if you had initiated such a legislative reform just a few years ago OSM would have been under the Creative Commons BY-SA—which is incompatible with OSM’s current license, the ODbL. Remember how much grief has resulted from the unclear (or perhaps too clear) licensing status of ZFS on Linux? Releasing software and data under the freest, most permissive license possible prevents such a thing from ever happening. I would rather allow a hundred Chinese featurephone vendors to lock down their crappy derivatives of my code than use my copyright to prevent a free software project from using my code in good faith.
- cyphar 10y ago
  I view it as a personal choice for what you find important. Personally, I would prefer that my software not be used rather than it be used in a way that takes away users' freedom. You clearly think differently and are entitled to think differently. Maybe you might consider using the MPLv2? It's a weak copyleft license that allows sub-licensing to other copyleft licenses (and inclusion into lax licensed projects without re-licensing the original project). Unfortunately, it suffers from not being strong enough to cover a "derived work" and only effectively copylefts files. But IMO that's better than nothing.
dec0dedab0de 10y ago
I think the best explanation of the differences between Free Software, Open Source, and Copy Left is the first 30 minutes of Revolution OS. This part for copyleft, does anyone really find this difficult to understand? https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s
snambi 10y ago
"Permissive" licenses provide highest freedom to "distributors". "Copyleft" licenses provide highest freedom to "end-users". "distributors" normally tend to be corporations that want to benefit from "free" software, but OTOH deny the same freedom to their own users. In other words, software that uses free software internally, but it itself was a proprietary with stringent license terms.

52 points by gexos 10y ago

> I prefer to think of the distinction in this way: permissive licenses provide the maximum freedom for downstream developers (including the ability to use the open source code in a closed source project), whereas copyleft licenses provide the maximum freedom for downstream users. This is a common analogy but it never sits well with me. Really, the permissive licenses allow the code to show up in places that copyleft licenses would not allow it. There are a ton of open source projects used in Microsoft Windows or iOS thanks to their permissive licensing -- and neither Microsoft nor Apple are legally obliged to give anything back. Copyleft licenses prevent the software from being forked into a proprietary program and the changes hidden from the user. To take a random example, if Microsoft took GNU gzip and included it with Windows, and then extended it with new features, Microsoft would be obliged to provide the source code to those changes. If they took OpenBSD's implementation instead, they wouldn't be obliged in the same way (though they still _could_). Remaining entirely in the open source world, these licenses concern redistribution of software. A user on OpenBSD does not feel they have any less freedom than a user on GNU/Linux. They don't have any less freedom, after all. Users on both systems retain the full gamut of freedom. To run for any purpose, to study the source code, to modify the source code, to redistribute the software verbatim or modified. The difference shows up when it comes to this: Do you want to be an asshole? OpenBSD permits the option -- you can distribute a fork without the source code. You cannot do that with a GPL-licensed system. The FSF and other GPL advocates usually ride on the premise that opening up the possibility for downstreams to be assholes is bad, with few exceptions. I do respect their opinions, but I feel like the history of open source (and the *BSDs, even) show that such assholes don't get very far. They simply cannot compete with the pace of open and transparent development and die off on their own. Frankly, being an asshole is an irrational and unprofitable (socially and commercially) move, and trying to nanny the behavior away isn't all that necessary.

Flimm 10y ago
You're comparing users of OpenBSD to users of GNU/Linux, but why not compare both of them to users of Windows and OS X? Why is FLOSS software pitted against each other, instead of FLOSS software against proprietary and closed source software?
- chungy 10y ago
  I'm sorry, I didn't mean to pit them against each other, just pointing out that users of either system enjoy the same freedoms regardless of the license choices. :-) Windows, OS X, iOS, and all other proprietary systems do, in fact, restrict users and objectively have fewer freedoms than free ones.
  - AimHere 10y ago
    And there is, or was, BSD code in both Windows and OSX, some of which was locked off in proprietary parts. OSX also contains some GPLed code, all of which is available to the user under righteous free software terms (as is at least some of their permissive-licensed code). The problem that Stallman and the FSF complain about isn't the relative freedom of the users of OpenBSD and GNU/Linux, but what happens to the freedoms of users who are further downstream.
vertex-four 10y ago
There's not a small number of cases where people's work was coopted to create successful proprietary software. JunOS is closed-source and based on FreeBSD - the PS4's OS similarly so. When I went scrolling through an old iPod's copyright page, there's an incredible amount of MIT/BSD-licensed software in there. And so on and so forth.
JackdawX 10y ago
> Really, the permissive licenses allow the code to show up in places that copyleft licenses would not allow it. There are a ton of open source projects used in Microsoft Windows or iOS thanks to their permissive licensing -- and neither Microsoft nor Apple are legally obliged to give anything back. This whole sentence is backwards isn't it? A libre license does not restrict code from being used by Microsoft or Apple, it is those companies that restrict their developers from using libre licensed code. The license doesn't care who uses it. Apple used the GCC project as their primary compiler for many years, contributing objective-c to it.
ent 10y ago
Copyleft licenses are more about the freedom of users in the future, instead of now. If all software was mit/bsd licensed, there wouldn't be any need for gpl as anyone could modify and redistribute any piece of software freely. Gpl is intended to force us toward that state in the future.
cyphar 10y ago
> I feel like the history of open source (and the BSDs, even) show that such assholes don't get very far. Some versions of the SONY PlayStations are based on FreeBSD. The users of said PlayStations don't have any software freedom because the entire OS is proprietary. Assholes like this do exist, and if FreeBSD (and the other BSDs) were copylefted this wouldn't have happened. There are other examples (essentially any example of a company using BSD as the basis for their OS), but the point is pretty clear IMO.

bkuhn 10y ago

Those who wish to learn more about copyleft after reading Ben's article may also want to look at the copyleft guide https://copyleft.org/guide https://copyleft.org/guide for more information. Ben is a contributor to the copyleft guide, so we'll likely merge in his article into the Guide.

dhimes 10y ago

Can you make money writing and selling copyleft-licensed software? The licenses always appeared to me to make that difficult. I write one, sell it, and the purchaser can now give it away for free. But I probably just don't understand it.

cyphar 10y ago
The same argument is true for any free software. If you sell free software, then the purchaser necessarily must have the freedom to distribute said software. So copyleft hasn't changed anything in that regard. And there are several companies that sell free (and even copylefted) software. SUSE and RedHat are the prime examples -- the way it works is that you sell support licenses. So if they want to get L3 support for a bug they found (or want you to work on a new feature) they have to pay you. It's a fairly simple model (though more complicated than the standard proprietary model of "my binaries are holy and you must pay me for them" -- which I always found to make no sense because software isn't a real thing).
- dhimes 10y ago
  I was really asking a question, but I think I understand your answer. I can see where there is a business case for it, but also the other. As an example from another field, my architect drew up plans for my house. I'm only allowed to use those plans for that house. I can't build another house just like it, and I can't sell the plans to somebody else. His expertise and hard work went into making the plans. It's no more "real" than a print-out of a program. Yet it would be very hard for him to make a living if other architects could just take his plans and use them. And the idea of selling giving the program away for free but charging to fix the errors may not be the best for all cases. I can see the case for copyleft, but I don't think it's the only case. (Not that you said it was- in fact, I've heard some people say something like that but not too many.)
  - cyphar 10y ago
    > I can't build another house just like it, and I can't sell the plans to somebody else. That wouldn't be considered "free software" if house designs were the same as software. But they aren't -- software serves a functional purpose and is something you use constantly throughout your life. House plans are essentially used once to build your house and that's about it. Though of course you could argue that an architect could have a business model that allows for their clients to resell the plans (by selling customisations to plans or creating new plans for each customer). > Yet it would be very hard for him to make a living if other architects could just take his plans and use them. It would also be hard for "users" of the plans to be able to ask for another architect's opinion on the plans. Or to say "this architect is not doing as I say, I will take these plans to someone else who can help me better". > And the idea of selling giving the program away for free but charging to fix the errors may not be the best for all cases. You can also sell improvements or features. In fact, you can get contract work with people paying you to implement features in $freeSoftwareProject. Sure, it's not a very common model but it does exist. > but I don't think it's the only case. It's not the only case, but as a developer it's the case I always aim for. Licensing something under a lax license is generally a tactical move (it would be a greater benefit if this wasn't copylefted), but I personally will always opt for copyleft because then I can guarantee that the eventual users of my software will have freedom.

anjbe 10y ago

Discussions of copyleft versus permissive licensing always seem to cover the same “freedom for users versus freedom for developers” clichés and the same tired slavery metaphors. My dislike of copyleft is emphatically not because I want to enable proprietary software. I hate proprietary software, and don’t use it on my machines. No, my biggest complaint about copyleft has always been that it prevents other free software from being able to use it. Copyleft licenses actively lead to incompatibility. Remember when LibreDWG, an AutoCAD file parser, couldn’t be used in various free software CAD projects, because LibreDWG is GPLv3+ and FreeCAD, etc were GPLv2 only? http://libregraphicsworld.org/blog/entry/libredwg-drama-the-end-or-the-new-beginning http://libregraphicsworld.org/blog/entry/libredwg-drama-the-... If FreeCAD had been under a permissive license, it would have been able to link against LibreDWG. If LibreDWG had been under a permissive license, FreeCAD would have been able to link against it. If they were both under a permissive license, they would have been able to be linked together and share code directly! How about when NYC released open building and address data? A laudable move, one that helped several open source projects, the largest probably being OpenStreetMap. OpenStreetMap is under a copyleft license, and though they benefit from NYC’s data, due to the licensing NYC can’t make use of OpenStreetMap’s improvements without a convoluted parallel construction scheme: https://www.openstreetmap.org/user/lxbarth/diary/23588 https://www.openstreetmap.org/user/lxbarth/diary/23588 A common response is that the onus is on NYC to release their data under a copyleft license so they can benefit. But there are often significant (even legislative!) barriers to doing that, especially in the United States where government entities are often required to release data to the public domain. How about changing that legislation? Well, if you had initiated such a legislative reform just a few years ago OSM would have been under the Creative Commons BY-SA—which is incompatible with OSM’s current license, the ODbL. Remember how much grief has resulted from the unclear (or perhaps too clear) licensing status of ZFS on Linux? Releasing software and data under the freest, most permissive license possible prevents such a thing from ever happening. I would rather allow a hundred Chinese featurephone vendors to lock down their crappy derivatives of my code than use my copyright to prevent a free software project from using my code in good faith.

cyphar 10y ago
I view it as a personal choice for what you find important. Personally, I would prefer that my software not be used rather than it be used in a way that takes away users' freedom. You clearly think differently and are entitled to think differently. Maybe you might consider using the MPLv2? It's a weak copyleft license that allows sub-licensing to other copyleft licenses (and inclusion into lax licensed projects without re-licensing the original project). Unfortunately, it suffers from not being strong enough to cover a "derived work" and only effectively copylefts files. But IMO that's better than nothing.

dec0dedab0de 10y ago

I think the best explanation of the differences between Free Software, Open Source, and Copy Left is the first 30 minutes of Revolution OS. This part for copyleft, does anyone really find this difficult to understand? https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s

snambi 10y ago

"Permissive" licenses provide highest freedom to "distributors". "Copyleft" licenses provide highest freedom to "end-users". "distributors" normally tend to be corporations that want to benefit from "free" software, but OTOH deny the same freedom to their own users. In other words, software that uses free software internally, but it itself was a proprietary with stringent license terms.