@davidrevoy >But isn't it complex to patch a license with a custom exception for end users?
It isn't a license patch - it's an license exception that is quite trivial to add to the license notice.

With brushes under AGPLv3-or-later+Brushes-Exemption, on viewing the license (what they should do), the user will immediately know that the AGPLv3-or-later applies to the brushes, but not the works drawn with the brushes.

>creative assets
creative works

>We concluded it's safer for users to have (brushes, textures, patterns) in CC-0/Public Domain.
Unfortunately, legally it's less safe for the users, as public domain doesn't really exist in many countries and I'm not that confident in the validity of the fallback license in such countries and CC0 also explicitly doesn't grant a patent license (which is not relevant in this case, but can burn people in other cases).

I'm more confident in the validity of the WPDD; https://wpdd.info/ but unfortunately it isn't ready yet.