Assume I have a python script that runs a GPL library binary through command line (through os.system('GPL call') and then analyze the output (which comes from the terminal). Is that a collaborative work? If so, does the GPL library apply as the all code? Or is it considered linking?

1 Answer 1


Firstly, IANAL/IANYL, and the whole question of derivative works is still somewhat unsettled by courts around the world.

That said, the FSF addresses this issue with respect to plugins, and since copyright law makes no explicit mention of plugins as being special, the analysis can be applied to other questions of derivative works. They write:

A main program that uses simple fork and exec to invoke plug-ins and does not establish intimate communication between them results in the plug-ins being a separate program.

though they also note that

If the main program uses fork and exec to invoke plug-ins, and they establish intimate communication by sharing complex data structures, or shipping complex data structures back and forth, that can make them one single combined program.

So if this is honest fork-and-exec, that is if your program invokes the GPL program through a system call and no additional complex, programme-specific structure is passed around the back, then the two works are separate.

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    At least, the FSF thinks they're separate. The FSF has no power to dictate what is or is not a derivative work which is entirely a matter of law and can even differ between jurisdictions. Commented Sep 3, 2017 at 23:22
  • 2
    @DavidSchwartz quite so, which is why I started by pointing out that no-one knows exactly what makes a derivative work, because the copyright treaties don't spell it out and many nations have no binding case law as yet. That said, when it comes to GPL interpretation (which is what this question is about) some courts have found the FSF's views to be informative, though by no means binding. Thus I figure that if the FSF says you're on safe ground, you probably are. Better than that I think we can't do, though I'd love to read your alternative answer if you have one.
    – MadHatter
    Commented Sep 4, 2017 at 6:49
  • @DavidSchwartz, for this forum I think the only relevant community/jurisdiction is US-EU.
    – Pacerier
    Commented Sep 11, 2022 at 22:05
  • @Pacerier For what it's worth, the test under US law is whether the python script itself contains sufficient protectable expression taken from the work that is licensed under the GPL. Of course, while the test is crystal clear, exactly how you decide what constitutes protectable expression that has been taken and how much is needed to be sufficient is not clear at all. Commented Sep 11, 2022 at 22:55
  • @Pacerier Conceptually, it's no different from me writing a space novel and Disney suing me for taking too much from their Star Wars franchise. The legal question is what can be found in my novel that is protectable expression from the Star Wars franchise and once all of that is identified, is it sufficient to constitute infringement? This can include things like characters, settings, dialog, and so on -- anything copyright can protect (so not ideas or functions). Commented Sep 11, 2022 at 22:58

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