How to license free assets but prevent asset flipping?

Question

I'm a hobbyist prop artist and give away everything I make for free, even for commercial use. At the moment I use the CC BY 4.0 license which is great except for the fact that someone would be able to download my assets and sell unmodified for a profit.

Ideally, I would like a license where you are free to download and use my assets for free but can only be used for commercial purposes where the assets are not the primary focus of the product e.g. included as part of a game.

Does anyone have any experience here about how best to achieve this?

Answer 1

Whether an asset is in "primary focus" is a fairly subjective criterion, which is difficult to capture in a license text. You could crayon one and have it checked by a lawyer, but crayon licenses have the usual potential pitfalls.

I would suggest releasing them with CC BY-NC 4.0 (the "NC" stands for "non-commercial"), and also advertising that you provide free commercial licenses on a case-by-case basis.

Doing this would partially defeat the point of a public license—by making all potential commercial users have to contact you—but you could then easily vet all applicants yourself by your criteria, without having to figure out how to translate them into legalese and worry about whether you did so correctly.