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So QML and QT design tools are awesome! I think nothing matches the capabilities of this platform. Still, each time I think of using QT I get discouraged (a bi

So QML and QT design tools are awesome! I think nothing matches the capabilities of this platform. Still, each time I think of using QT I get discouraged (a bit) by the licensing (even though there's almost zero chance I'll ever independently sell a software product! :-p). In paper, one should be able to use the community version of QT for commercial software, but it looks like actually doing this could be really tricky [1]. And the commercial license is so expensive! QT page says: "Pricing starts at $459/mo." :-O. 1: https://www.quora.com/Can-I-use-the-free-QT-for-c++-commercially https://www.quora.com/Can-I-use-the-free-QT-for-c++-commerci...

nabla9 8y ago
How is it tricky? Unless you start to mess with the QT libraries directly, there should be no problems whatsoever. You just attach unmodified object files and/or source code (as you did not make changes to them) into the software distribution.
irishcoffee 8y ago
Qt is lgpl. Unless I missed something, this should not be a problem whatsoever if you'd like to use the Qt framework and sell commercial software.
- hjek 8y ago
  Exactly. No problem whatsoever selling something made using Qt[0]. But there is a "problem" using Qt to release proprietary software, of course, because Qt is free, and perhaps parent isn't aware of the distinction between commercial and proprietary? [0]: https://www.gnu.org/philosophy/selling.html https://www.gnu.org/philosophy/selling.html
  - SwellJoe 8y ago
    LGPL is not GPL. You're adding to the confusion by conflating them.
  - munk-a 8y ago
    This is incorrect, using LGPL licensed software does not prevent you from keeping your software closed source, any components you rely on from Qt will need to be provided (or reference given which is a _really_ weak requirement) in open source but any functions referencing Qt functions do not themselves need to be provided in a decompiled form, this is pretty much why LGPL exists. So if you're company is trying to make money making proprietary improvements to Qt _which require you to edit Qt_ then you're a bit hooped, but I strongly suspect instead there was a misunderstanding which how contagious free software is. (That said, whenever possible please give back to the FSF community)
    - berti 8y ago
      Does #including (non-trivial) Qt headers make your software a derivative work? IIRC there is a decent amount of actual code in some of the headers. Seems like a very grey area.
      - deleted 8y ago
        [deleted]
      - munk-a 8y ago
        It does not, and with significantly complex header files (like the SIGNAL/SLOT macros Qt includes) this can seem like a grey area, but the LGPL specifically splits code into object & specification code, if your code directly references and links against publicly defined specification code you're in the clear... if you are doing this with knowledge of how specific object code works and manipulating that object code using your own code (i.e. intentionally overwriting a stake frame) I think that does become more of a grey area, but the intent of the license is very straightforward about allowing non-contagious use of interface specifications, that is what specifically makes it LGPL instead of GPL (the latter lacks that distinction and does not allow the use you're asking about among some other uses). This is of course complicated by SaaS and all that is covered in more detail in Affero license and in that field I'm out of my depth. Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional.
- StavrosK 8y ago
  Can someone tell me in simple terms what the Qt licensing situation is? The webpage for Qt Design Studio says you can only use the designs you come up with in an app if you have a Qt commercial license.
  - cpburns2009 8y ago
    It looks like Qt Design Studio is a commercial product that's free for evaluation only. > Qt Design Studio is available today as a free tool for everyone to try out and evaluate. You will need a commercial Qt developer license to distribute your UIs created with Qt Design Studio. > We are also working on an open source version with a limited feature set, to be published in December. The Qt library itself has both commercial and LGPL licenses. You can safely use LGPL libraries in commercial products with a couple obscure provisions: it's commonly held the library has to be dynamically linked, the user has the right to replace the Qt dynamic libraries, and maybe a few other inconsequential things.
- mrpippy 8y ago
  Specifically, LGPL3 since Qt 5.7. Big problem for people making embedded devices, but shouldn’t be for commercial software.
  - exikyut 8y ago
    If the embedded device supports dynamically linked libraries, though, that could still work
    - joezydeco 8y ago
      As long as you can deliver the toolchain used to build the libraries, and allow the finished libraries to be installed on your target hardware over the current ones. I know one major vehicle manufacturer that won't go past 5.6 because of this reason. They put it right in the RFP.
      - reitanqild 8y ago
        Edit: I might be misunderstanding something here but: I'd think a major vehicle manufacturer should be able to pay for the commercial license?
        joezydeco 8y ago
        Has nothing to do about the royalty fees. Those didn’t change from 5.6 to 5.7. It has everything to do with being required to allow end customers to install their own libraries on a piece of their machinery. LGPL 3 closed the LGPL 2.1 loophole concerning this. The legal and warranty issues around letting customers reflash their dashboards are what the company wants to avoid.
        reitanqild 8y ago
        But I thought that was part of what you got with the commercial license, a right to use it without adhering to the open source license?
emmanueloga_ 8y ago
re: people asking "how is this tricky" or "am I missing something"... really read the Quora answer :-)
- munk-a 8y ago
  I have really read the Quora answer, is this an issue with understanding how LGPL licensing works? It does have some complications but the common approach when compiling a binary involving large precompiled libraries the .so/.dll objects will be excluded direct inclusion in the binary and kept as linked objects. I certainly can understand this being a bit hazy for people not used to working with compiled languages and that goes double for lawyers but this is a well established approach.
- int_19h 8y ago
  The answer on Quora is also rather alarmist. Plenty of startups use LGPL'd software without any issues. Yes, you will need to be aware of it, and disclose it as needed. Same with any other bit of open source. So?
im_down_w_otp 8y ago
A decent developer is ~$15,000/mo after taxes and benefits, give or take. Does the toolkit provide you capability or efficiency gains at 1/30th that which an extra developer would? If so, then it would seem to be well worth it.
- exikyut 8y ago
  Define "decent". I'm very curious to hear this. (Completely out of touch with the field.)
  - im_down_w_otp 8y ago
    Doesn't bring ego into their work, can flexibly learn things quickly to identify and then use the right tools for the job, isn't driven by the fad-of-the-day unless there's legitimate (not contribute) merit to said fad applied to their problem, decreases the amount of immutable calcified process/design/implementation debt over time rather than increasing it, and knows on their own how & when to balance being a framer vs. a finisher.
- trymas 8y ago
  > decent developer Working in (or for a company from) a very expensive/rich technological hub of the world, i.e. couple of places in US, couple in Europe and couple in Asia. At least in Europe "decent" would mean "top 1%" - because it translates to ~300k€+ before taxes.
  - distances 8y ago
    I think you read the parent wrong, they meant $15k total expense to employer, so $180k per year. I don't know how large are the US employment costs in addition to the salary, but assuming 40%, the employee would see ~$130k before taxes. Way above "decent" engineer salary for the rest of the world, but I guess that's plausible in US?
    - im_down_w_otp 8y ago
zurn 8y ago
Your quoted link points out no actual problems? It just conveys a fearful mystic vibe about the license and then reduces to "if you get acquired, the lawyers might want to look into the LGPL and it might cause a delay, thus hurting the acquisition". Maybe this person has not read the LGPL, it's an easy read.

nabla9 8y ago

How is it tricky? Unless you start to mess with the QT libraries directly, there should be no problems whatsoever. You just attach unmodified object files and/or source code (as you did not make changes to them) into the software distribution.

irishcoffee 8y ago

Qt is lgpl. Unless I missed something, this should not be a problem whatsoever if you'd like to use the Qt framework and sell commercial software.

hjek 8y ago
Exactly. No problem whatsoever selling something made using Qt[0]. But there is a "problem" using Qt to release proprietary software, of course, because Qt is free, and perhaps parent isn't aware of the distinction between commercial and proprietary? [0]: https://www.gnu.org/philosophy/selling.html https://www.gnu.org/philosophy/selling.html
- SwellJoe 8y ago
  LGPL is not GPL. You're adding to the confusion by conflating them.
- munk-a 8y ago
  This is incorrect, using LGPL licensed software does not prevent you from keeping your software closed source, any components you rely on from Qt will need to be provided (or reference given which is a _really_ weak requirement) in open source but any functions referencing Qt functions do not themselves need to be provided in a decompiled form, this is pretty much why LGPL exists. So if you're company is trying to make money making proprietary improvements to Qt _which require you to edit Qt_ then you're a bit hooped, but I strongly suspect instead there was a misunderstanding which how contagious free software is. (That said, whenever possible please give back to the FSF community)
  - berti 8y ago
    Does #including (non-trivial) Qt headers make your software a derivative work? IIRC there is a decent amount of actual code in some of the headers. Seems like a very grey area.
    - deleted 8y ago
      [deleted]
    - munk-a 8y ago
      It does not, and with significantly complex header files (like the SIGNAL/SLOT macros Qt includes) this can seem like a grey area, but the LGPL specifically splits code into object & specification code, if your code directly references and links against publicly defined specification code you're in the clear... if you are doing this with knowledge of how specific object code works and manipulating that object code using your own code (i.e. intentionally overwriting a stake frame) I think that does become more of a grey area, but the intent of the license is very straightforward about allowing non-contagious use of interface specifications, that is what specifically makes it LGPL instead of GPL (the latter lacks that distinction and does not allow the use you're asking about among some other uses). This is of course complicated by SaaS and all that is covered in more detail in Affero license and in that field I'm out of my depth. Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional.
StavrosK 8y ago
Can someone tell me in simple terms what the Qt licensing situation is? The webpage for Qt Design Studio says you can only use the designs you come up with in an app if you have a Qt commercial license.
- cpburns2009 8y ago
  It looks like Qt Design Studio is a commercial product that's free for evaluation only. > Qt Design Studio is available today as a free tool for everyone to try out and evaluate. You will need a commercial Qt developer license to distribute your UIs created with Qt Design Studio. > We are also working on an open source version with a limited feature set, to be published in December. The Qt library itself has both commercial and LGPL licenses. You can safely use LGPL libraries in commercial products with a couple obscure provisions: it's commonly held the library has to be dynamically linked, the user has the right to replace the Qt dynamic libraries, and maybe a few other inconsequential things.
mrpippy 8y ago
Specifically, LGPL3 since Qt 5.7. Big problem for people making embedded devices, but shouldn’t be for commercial software.
- exikyut 8y ago
  If the embedded device supports dynamically linked libraries, though, that could still work
  - joezydeco 8y ago
    As long as you can deliver the toolchain used to build the libraries, and allow the finished libraries to be installed on your target hardware over the current ones. I know one major vehicle manufacturer that won't go past 5.6 because of this reason. They put it right in the RFP.
    - reitanqild 8y ago
      Edit: I might be misunderstanding something here but: I'd think a major vehicle manufacturer should be able to pay for the commercial license?
      - joezydeco 8y ago
        Has nothing to do about the royalty fees. Those didn’t change from 5.6 to 5.7. It has everything to do with being required to allow end customers to install their own libraries on a piece of their machinery. LGPL 3 closed the LGPL 2.1 loophole concerning this. The legal and warranty issues around letting customers reflash their dashboards are what the company wants to avoid.
        reitanqild 8y ago
        But I thought that was part of what you got with the commercial license, a right to use it without adhering to the open source license?

emmanueloga_ 8y ago

re: people asking "how is this tricky" or "am I missing something"... really read the Quora answer :-)

munk-a 8y ago
I have really read the Quora answer, is this an issue with understanding how LGPL licensing works? It does have some complications but the common approach when compiling a binary involving large precompiled libraries the .so/.dll objects will be excluded direct inclusion in the binary and kept as linked objects. I certainly can understand this being a bit hazy for people not used to working with compiled languages and that goes double for lawyers but this is a well established approach.
int_19h 8y ago
The answer on Quora is also rather alarmist. Plenty of startups use LGPL'd software without any issues. Yes, you will need to be aware of it, and disclose it as needed. Same with any other bit of open source. So?

im_down_w_otp 8y ago

A decent developer is ~$15,000/mo after taxes and benefits, give or take. Does the toolkit provide you capability or efficiency gains at 1/30th that which an extra developer would? If so, then it would seem to be well worth it.

exikyut 8y ago
Define "decent". I'm very curious to hear this. (Completely out of touch with the field.)
- im_down_w_otp 8y ago
  Doesn't bring ego into their work, can flexibly learn things quickly to identify and then use the right tools for the job, isn't driven by the fad-of-the-day unless there's legitimate (not contribute) merit to said fad applied to their problem, decreases the amount of immutable calcified process/design/implementation debt over time rather than increasing it, and knows on their own how & when to balance being a framer vs. a finisher.
trymas 8y ago
> decent developer Working in (or for a company from) a very expensive/rich technological hub of the world, i.e. couple of places in US, couple in Europe and couple in Asia. At least in Europe "decent" would mean "top 1%" - because it translates to ~300k€+ before taxes.
- distances 8y ago
  I think you read the parent wrong, they meant $15k total expense to employer, so $180k per year. I don't know how large are the US employment costs in addition to the salary, but assuming 40%, the employee would see ~$130k before taxes. Way above "decent" engineer salary for the rest of the world, but I guess that's plausible in US?
  - im_down_w_otp 8y ago

zurn 8y ago

Your quoted link points out no actual problems? It just conveys a fearful mystic vibe about the license and then reduces to "if you get acquired, the lawyers might want to look into the LGPL and it might cause a delay, thus hurting the acquisition". Maybe this person has not read the LGPL, it's an easy read.