Pondering Licening

Pondering Licening

(I am not a lawyer, this is not legal advice.)

I was looking into using CC-BY-SA art from here on Open Game art for use in a project. It appears it cannot be used with Unreal Engine or Unity, because neither of them are distributed under a CC-BY-SA compatible license. Releasing a game with CC-BY-SA or GPL licensed content would require the engine source to be released under the same license. This would also include such content as the Unity logo, Unreal logo, or any other trademarks, if they are displayed in your game or it's icon.

On UE4 Answerhub, a staff member clears this up here: https://answers.unrealengine.com/questions/345491/why-is-denied-creative...

The unity engine source code is only released under this license: https://unity3d.com/legal/licenses/Unity_Reference_Only_License

So I guess this means we can't use any game engines that aren't CC0 or CC-SA, since they would contain proprietary code not developed by us? Even if we were to release our game under CC-BY-SA? What game engines have been released under CC0 or CC-SA?

If we take this a step further, does this mean we wouldn't be able to, for example, use any Microsoft binaries in our game (.Net Framework components, like System.Collections) or Mono components (in the case of Unity)? Exactly how far up the chain does this go?

If the asset is released under CC-BY-SA 4.0 (not 3.0) that would at least include GPLv3 licensed engines (https://creativecommons.org/share-your-work/licensing-considerations/com...).

I have searched a lot about licensing on these forums, and have seen a lot of good arguments for both sides. In my opinion, Epic's answer (in the link) is the most authoritative I've seen, as they would have developed this policy in coordination with their legal team.

If every Unreal or Unity developer was scrupulous and followed every license accurately, this excludes a large portion of OGA.

Everything licensed under a CC-BY-SA or GPL License would be out of the question. Only the OGA-BY, CC non-SA, and the LGPL licensed content would be doable. This leaves roughly 20% of the assets unusable.

So I guess my question is... Am I interpreting all of this correctly? And if I am, are these licenses actually bad for game or software assets of any kind?

edit: fixed a word substitution error