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This is an open question. The GPL itself does not define what constitutes a derivative work. The FSF does, however, promote the view that linking does create a

This is an open question. The GPL itself does not define what constitutes a derivative work. The FSF does, however, promote the view that linking does create a derivative work, while simply calling an external binary in usual cases does not. But that can't function as a hard rule. Because I could just make a wrapper binary that handles all of the scenarios I need a GPL'd library for, and then call my wrapper executable from my proprietary code.

jahewson 9y ago
> Because I could just make a wrapper binary that handles all of the scenarios I need a GPL'd library for, and then call my wrapper executable from my proprietary code. Yes, you can literally do this. It's not a derived work because your code is entirely independent of the GPL'd code and the GPL can't possibly cover code that you wrote independently. Simply interacting with some external GPL'd program does not expose your code to any GPL requirements.
- marcoperaza 9y ago
  You can't just work around the GPL by placing a command-line interface as a shim between your code and the function call interface of the GPL'd library. I'm talking about a contrived binary that just calls library functions, forwarding command line parameters to the arguments of that function as necessary.
  - jahewson 9y ago
    Oh yes you can. The GPL gets its power from copyright - the rights that the authors of the original software have over their work. It does not and cannot place any restrictions on any software that you write, unless you literally incorporate the GPL'd source or binary into your software, which a CLI interface does not. The same would be true of an RPC interface. For example, many databases are GPL'd and provide their entire functionality over RPC. Many CLI programs are GPL'd and (of course) provide their entire functionality over CLI. Neither of these cases place GPL obligations on clients, and it's no different for any given library which you wrap with a CLI.
    - marcoperaza 9y ago
      The FSF disagrees with you. https://www.gnu.org/licenses/gpl-faq.html#GPLInProprietarySystem https://www.gnu.org/licenses/gpl-faq.html#GPLInProprietarySy... A contrived wrapper that is not an independently useful program does not allow you to circumvent the GPL. You are leaning very heavily on a technical distinction (linking vs. not linking) instead of on a holistic analysis of what a "derived work" is.
      - michaelmrose 9y ago
        Pretty sure the FSF can't magically extend what copyright means to comport with what they think it ought to mean in regard to free software.
        adament 9y ago
        Now I am not a lawyer, but I think by analogy the FSFs interpretation would also be needed to enforce the CreativeCommons NoDerivatives licenses. Imagine someone creates an interview-based documentary video series on a controversial scientific topic say global warming and releases it under a NoDerivatives license because they are afraid that a clever edit of their videos would present the topic incorrectly and they have made promises to the scientists about how they will and will not present them. Now imagine that I rather than edit the video files themself create a playlist, in a (fictive?) format which has the ability to play subsequences of the linked files, and then creates a version of the series which presents the complete opposite message of the original. Would a court find this to be a derivative work of the original videos? What if in my need to edit the video I want to insert certain new short sequences, and thus I distribute a second video along with the playlist, but this video is useless in itself since it just contains a number of short clips in sequence. Would this video be considered a derivative work of the original - remember it serves no purpose in itself except along with the playlist and the original? To me it is not clear, but if they are not derivatives, then this will practically render the concept moot. Since most derivatives could potentially be formulated as the original + a diff. Now I would expect in this case that the combination of the playlist + my video file + original series be considered a derivative work, remember that in the arts transferring a work from one format to another (a dramatization for example) is considered to be a derivative work, even if all the actors would be seen on stage to read from the original book. As I read it, this is the center of the FSFs argument. Now whether this would apply equally to software I do not know. But I have a hard time imagining that copyright is not as easily circumvented as you seem to indicate.
  - michaelmrose 9y ago
    Can you substantiate that claim?
    - lomnakkus 9y ago
      What claim? I think it's pretty obvious that the GPL derives it's power from copyright. Reasoning: If the GPL does not apply, then you don't have any right to anybody else's code (by the Berne Convention), so it gets its power by granting you more rights than you would have had by default. Make sense?

jahewson 9y ago

> Because I could just make a wrapper binary that handles all of the scenarios I need a GPL'd library for, and then call my wrapper executable from my proprietary code. Yes, you can literally do this. It's not a derived work because your code is entirely independent of the GPL'd code and the GPL can't possibly cover code that you wrote independently. Simply interacting with some external GPL'd program does not expose your code to any GPL requirements.

marcoperaza 9y ago
You can't just work around the GPL by placing a command-line interface as a shim between your code and the function call interface of the GPL'd library. I'm talking about a contrived binary that just calls library functions, forwarding command line parameters to the arguments of that function as necessary.
- jahewson 9y ago
  Oh yes you can. The GPL gets its power from copyright - the rights that the authors of the original software have over their work. It does not and cannot place any restrictions on any software that you write, unless you literally incorporate the GPL'd source or binary into your software, which a CLI interface does not. The same would be true of an RPC interface. For example, many databases are GPL'd and provide their entire functionality over RPC. Many CLI programs are GPL'd and (of course) provide their entire functionality over CLI. Neither of these cases place GPL obligations on clients, and it's no different for any given library which you wrap with a CLI.
  - marcoperaza 9y ago
    The FSF disagrees with you. https://www.gnu.org/licenses/gpl-faq.html#GPLInProprietarySystem https://www.gnu.org/licenses/gpl-faq.html#GPLInProprietarySy... A contrived wrapper that is not an independently useful program does not allow you to circumvent the GPL. You are leaning very heavily on a technical distinction (linking vs. not linking) instead of on a holistic analysis of what a "derived work" is.
    - michaelmrose 9y ago
      Pretty sure the FSF can't magically extend what copyright means to comport with what they think it ought to mean in regard to free software.
      - adament 9y ago
        Now I am not a lawyer, but I think by analogy the FSFs interpretation would also be needed to enforce the CreativeCommons NoDerivatives licenses. Imagine someone creates an interview-based documentary video series on a controversial scientific topic say global warming and releases it under a NoDerivatives license because they are afraid that a clever edit of their videos would present the topic incorrectly and they have made promises to the scientists about how they will and will not present them. Now imagine that I rather than edit the video files themself create a playlist, in a (fictive?) format which has the ability to play subsequences of the linked files, and then creates a version of the series which presents the complete opposite message of the original. Would a court find this to be a derivative work of the original videos? What if in my need to edit the video I want to insert certain new short sequences, and thus I distribute a second video along with the playlist, but this video is useless in itself since it just contains a number of short clips in sequence. Would this video be considered a derivative work of the original - remember it serves no purpose in itself except along with the playlist and the original? To me it is not clear, but if they are not derivatives, then this will practically render the concept moot. Since most derivatives could potentially be formulated as the original + a diff. Now I would expect in this case that the combination of the playlist + my video file + original series be considered a derivative work, remember that in the arts transferring a work from one format to another (a dramatization for example) is considered to be a derivative work, even if all the actors would be seen on stage to read from the original book. As I read it, this is the center of the FSFs argument. Now whether this would apply equally to software I do not know. But I have a hard time imagining that copyright is not as easily circumvented as you seem to indicate.
- michaelmrose 9y ago
  Can you substantiate that claim?
  - lomnakkus 9y ago
    What claim? I think it's pretty obvious that the GPL derives it's power from copyright. Reasoning: If the GPL does not apply, then you don't have any right to anybody else's code (by the Berne Convention), so it gets its power by granting you more rights than you would have had by default. Make sense?