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Given that I create a 3d model of a tree using a GPL plugin in GPL 3D software (Blender). The addon generates this 3d tree model from scratch, using an algorithm. No other external assets are used.

The original developer of this GPL plugin asserts that the generated 3d models cannot be shared, either free or commercially, and only be used in still and moving imagery.

Is this correct? Can the author of a GPL plugin attain control over what the user is allowed to do with the generated assets and assert copyright over these assets in this particular case?

  • Possible duplicate of Is the output of an open source program licensed the same? – Brandin Oct 24 '19 at 5:14
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    Also clarify whether your statement is hypothetical "The original developer of this GPL plugin asserts that the generated 3d models cannot be shared..." Did someone actually write a plugin and claim this as a term of use? Or is it just a hypothetical scenario? – Brandin Oct 24 '19 at 5:15
  • Possible duplicate of Is the output of an open source program licensed the same? – Mureinik Oct 24 '19 at 7:20
  • Yes, this is an actual sold plugin/add-on for Blender, which imports core parts of Blender's Python modules and is integrated fully in Blender, which makes it GPL. But the author does not mention this, and states the addon is his copyright and cannot be shared. He is breaking the GPL of Blender. – Herbert123 Oct 24 '19 at 10:06
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    @Herbert123 If he wrote the plug-in, then certainly he can copyright it and he can also sell it (the GPL does not forbid selling software). Whether he can publish his plug-in under a license other than the GPL, and whether or not he must release the source code to his plugin to paying customers are additional questions which you did not mention here. Besides, you didn't even clearly state whether or not he published his plugin as GPL or not. If he published the plugin as GPL and provided the source code to people who bought his plugin, then there is no GPL violation. – Brandin Oct 25 '19 at 6:25
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There are several levels of thing going wrong here.

Firstly, as Brandin notes above, with a few odd exceptions the licence of a program does not affect the licensing status of the output; the status of the output is much more usually a function of the licence on the program's inputs.

Secondly, if this is really a GPL-licensed plugin, then even if the output were in some way a copyright derivative of the program, both versions of the GPL would require that they be licenced under GPL (GPLv2 ss 1 and 2b, GPLv3 ss4 and 5b). The GPL, being a free licence, explicitly does not include any restrictions on usage and sharing (see freedoms zero and two). You don't say which version of the GPL it is, but GPLv3 explicitly forbids adding any such restrictions (GPLv3 s7), and GPLv2 disclaims any restrictions on usage (s0).

So I'm afraid this chap's claims don't stack up; even if his plugin does something odd like copying part of itself into the output, thus making the output a dervative of the program, his claim that the plugin is GPL-licensed rules out any non-GPL restrictions on subsequent usage, copying, and the like.

But as ever, IANAL/IANYL, so take professional legal advice before relying on this position.

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  • Thank you, I think this answers my question. Blender is licensed under GPL v3. The addon/plugin should be licensed likewise, but the developer asserts that the add-on is released under his copyright. And he forbids his users to share the 3d object output of his addon.This seemed to be incorrect, since Blender's license page states that: "What you create with Blender is your sole property. All your artwork – images or movie files – including the .blend files and other data files Blender can write, is free for you to use as you like." – Herbert123 Oct 24 '19 at 10:21
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Blender is licensed under the GPL, this also means that addon licenses need to be GPL compatible. The 3D models and artwork made by blender are not affected by the GPL.

But while the GPL does not affect the data generated by the program and/or addons, you should look into the addon a little more to see if the output data is generated or pre-bundled.

While the output generated by a GPL program is not affected by the programs license, there could be a catch where the program is modifying pre-existing data that is bundled as part of the source code which would fall under GPL. That would mean that the 3D models you save would fall under GPL. If on the other hand, the addon uses an algorithm to programmatically generate the trees, then the output would not be affected by the GPL. The fact that the addons developer says you cannot share the models, means they are either ignorant of how the GPL works, or know that you would be sharing data that was bundled under a GPL license.

If you are using bundled data that is GPL to generate a 2D image as output, then that image would not be GPL. Which is what the addons developer is saying is OK.

As a comparison, makehuman is released under AGPL, this program bundles pre-built mesh objects that the program modifies to your parameters. In this case, the project specifically states that the mesh data is released under CC0 so that there are no restrictions to the use of models output by the program.

As a special and limited exception, the copyright holders of the MakeHuman assets grants the option to use CC0 ... as a license for the MakeHuman characters exported ...

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  • The plugin uses an algorithm to generate trees, which means the output is not affected by the GPL even if the dev states "Do not sell or distribute 3D models of trees grown with The Grove." BUT: dev includes pre-modelled parts "twigs" which, if used, become part of the generated tree. These twigs would be his copyright, and when included, user is bound by this copyright not to share the 3d model. But using a twig is an OPTION. If the user creates a custom twig and a tree is generated with the custom twig or no twigs at all, I assume the tree can be shared (free or commercial). Correct? – Herbert123 Dec 1 '19 at 0:53
  • @Herbert123 I agree with you there, not using the devs "twig" models would separate you from the GPL. – sambler Dec 1 '19 at 4:44

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