Taking Artists Into Consideration

[Jason Self]

We actually already have what's being described there - strong copyleft
licenses that can be applied to art. The GPL can be used on any
copyrightable work, not just code. So the issue isn't that such
licenses don't exist. The real question is whether a particular use -
like a game built from CC BY-SA licensed stories or art - legally
counts as a derivative work under copyright to trigger those strong
copyleft obligations in the first place.

If it does, then a strong copyleft license already works as suggested:
the whole derivative would have to be released under the same license.
If it doesn't, then no copyright-based license can stretch that far
without trying to go beyond what copyright itself would otherwise
require. That's why I raised that question at the very end of the email
as to if that is the intention. And if it is...

Imagine if the image viewing program Viewnior (from MATE) were
considered a derivative of the images it displays. It's not, obviously,
but it shows how overbroad things could become if one makes a license
that any program displaying the image must itself by licensed under the
same license as the image itself, and a game engine could be doing
nothing more than what Viewnior does in terms of displaying a
copyrighted image during game play, and otherwise be completely
unrelated, copyright-wise.

So the real point of tension isn't about whether strong copyleft
licenses for art exist (they do), but whether what OP is really
proposing is a license that pushes obligations further than copyright-
based licenses would typically require such that it's not possible to
open the image in Viewnior to view it anymore without it turning into
some sort of license violation. And if it's okay for Viewnior to do
nothing more than display the image on screen then, to be consistent,
it has to be okay for a game engine to do exactly the same.