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I have a few questions about what users of my engine could copyright in their own project. The way the engine would work would be that it would be a standalone program in Java that would load all of the scripts/assets/data from a folder that the game takes place in. The code could be written in Python or compiled to Java.

Onto my questions, the code that they write would access some parts of my engine through Jython, and so I assume those would have to be released under the GPL. But what about the rest of the game other than the code? Like could they copyright their own art?

I guess what I really want is that modifications of the code of the engine must be released under the GPL, but projects created using my engine can be released under any copyright, as long as they obey they distribute the engine itself under the GPL.

asdf
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  • The GPL is complicated; is there a reason you want to even bother with it at all, versus a more simplified (and more reason, in my opinion) license? –  Dec 11 '14 at 20:21
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    Also note that copyright is implicit in the creation of a work (in the US at least); anybody who creates their own art retains the copyright to that art. The GPL (and other licenses) are mechanisms by which you, the copyright holder, license that work to others for use and reproduction. –  Dec 11 '14 at 20:23
  • Related question: GPL Game Engine - What needs to be released under GPL? – Anko Dec 11 '14 at 20:35

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No.

The GNU Public License is intentionally a viral license, which means derivative works must be distributed under the GPL also. Using your code as a library is a derivative work. Hence users of your game engine would need to release their game under the GPL also.

If you want to let your users choose a different license for their derivative work, but otherwise keep your code (and modifications to it) under a similar license, maybe you'd prefer the Lesser GNU Public License?

(IANAL.)

Anko
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  • You can dual license the work with parts being licensed under a different license. But only if you own the whole thing. – ratchet freak Dec 11 '14 at 22:23
  • Could downvoters explain? – Anko Dec 12 '14 at 20:42
  • I only just got here, but I think its because if the game engine is itself not modified in the creation of the specific game, those external scripts are not (necessarily) covered by the viral nature of GPL PL. The engine itself could be distributed by deathbutton1 and someone who makes a game with it could say "go download the engine, then put these scripts in the /game folder." At what point does GPL PL go "AH HA! THAT'S MINE TOO!"? Similiar question: If an image editing suite was GPL PL, would it virally infect the images created with it? What about plugins? Filter scripts? – Draco18s no longer trusts SE May 31 '17 at 16:14
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    @Draco18s The GPL infects code that links to GPL code (e.g. a game engine, or other library) into a single program. An image created with a GPL image editor doesn't link with the editor's code, so the GPL doesn't apply to the results. For the subtleties of what "linking" means, see the GPL guidelines on plug-ins, and the GPL linking exception. For a practical example, see Blender game licensing. – Anko Jun 01 '17 at 18:25
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the code that they write would access some parts of my engine through Jython, and so I assume those would have to be released under the GPL

I do not understand what makes you think so. Jython is not covered by GNU GPL and never was; its current release is under terms of Python Software Foundation License, which seems to be a lax permissive non-copyleft license, so just by using Jython you are not obliged to apply any specific license to your project (you even could make it non-free/proprietary).

According to your description:

...what I really want is that modifications of the code of the engine must be released under the GPL, but projects created using my engine can be released under any copyright...

the license that you really want apply to your work is GNU Lesser GPL.

Dmitry Alexandrov
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  • Thanks, I'll look into that. The whole licensing thing is really confusing, so ant help is appreciated. – asdf Dec 12 '14 at 16:23