> I imagine there might be (or could be) a license that asks for the "source" of art assets; that is, a .PSD file, or a blender project, or a script that generates the image. That's a lot more useful to me than the final image itself, and a lot easier to modify if I wanted.
This is used in the GPL :
"The “source code” for a work means the preferred form of the work for making modifications to it."
And also in the "open source definition" that can be used to judge whether something is free software or not :
"The source code must be the preferred form in which a programmer would modify the program." [1]