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I have written a software application and an accompanying software library. When users use this application, they will write code externally to it which also makes use of the software library. The application will then use the code that they have written.

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I have chosen to licence the library under the GNU GPL 3.0 licence. Please correct me if I am wrong, but my understanding is that the GPL 3.0 requires all derivative software to also be licenced under the GPL 3.0. This was a large reason for why I chose it. By releasing the library under GPL 3.0, so must all of the code written by users which makes use of it. This also means that my software application itself must be licenced under the GPL 3.0.

Am I able to break the rules of the GPL 3.0 and close-source/copyright the application while still having the library be GPL 3.0? If I do break the licence, can the licence remain enforceable for the software written by others?

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  • I’m voting to close this question because it's better asked at opensource.stackexchange.com
    – BlueDogRanch
    Commented Jun 18, 2020 at 17:58
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    @BlueDogRanch I was debating between the two. What makes you think it would be better there? In the end I chose here because my question isn't about the GPL specifically, but is about how the laws around it work.
    – Toby Smith
    Commented Jun 18, 2020 at 18:16
  • You can dual-license your software, releasing as GPL and keeping another license closed-source with whatever terms you want.
    – Ron Beyer
    Commented Jun 18, 2020 at 18:31
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    @BlueDogRanch "Better elsewhere" is not a valid close reason. "Off topic" is, but this is clearly a question about law.
    – Matt
    Commented Jun 18, 2020 at 18:54

2 Answers 2

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A license is a permission to let someone else use your software which would otherwise be subject to copyright (assuming you have correctly asserted copyright right by placing a valid copyright notice in a prominent place, e.g. "© Copyright 2018 Toby Smith, all rights reserved."). For the copyright be enforceable (i.e. a claim filed in court) in the US, it needs to be registered with the Library of Congress for a fee, though that can be done later.

However that permission does not put any constraints on what you want to do with the property. Perhaps you want to license it to someone else under a different license? Sure. The people using your software under license are obliged to follow the license or face a potential lawsuit for copyright infringement. You yourself are not bound by the license in the same way as the user, you are bond only in that you are promising not to sue the user of the software for copyright infringement if they use it in accordance with the terms of the license.

You may create derivative works and they would not be subject to GPL except if your original application is a derivative of someone else's GPL'd work, or you are using the modules created by your users, which could also be subject to GPL. To avoid any possible conflict of you breaking their license to you for use of their software, it might be prudent to obtain a separate (non GPL) license to use their modules.

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  • Thanks for the answer. The application will not be packaged/shipped/distributed alongside/using code written by users. The users will install the application and will then tell it where on their PC it can find their code for it to use. Does this still mean that the application is "using modules created by [my] users"? In theory they could supply it with code under any licence/copyright.
    – Toby Smith
    Commented Jun 19, 2020 at 9:24
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    If it is not distributed with, then no, it would not be using modules created by users. Yes, though there are some nuances around the GPL with relation to modules.
    – xirt
    Commented Jun 20, 2020 at 19:48
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You don’t need a licence to use your own IP

It’s yours, do what you like with it.

If you choose to licence your IP to particular people or the world at large they must follow the licence(s) you grant irrespective of what you or anyone else does.

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  • Loud and clear. I don't mean to nitpick but your answer doesn't directly answer my question. Are the terms of the licence still enforceable if I choose to break the terms of it myself?
    – Toby Smith
    Commented Jun 18, 2020 at 22:51
  • @TobySmith you don't break the licence simply because you (as the copyright owner) are not bound by it. Furthermore, you can issue a commercial licence to specific parties, and they won't need to care about the GPL either.
    – Greendrake
    Commented Jun 19, 2020 at 8:25

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