Thanks for the reply. We are not the copyright owners of the assets. Just a few months ago we implemented a CLA which would allow licensing using a later Creative Commons license version, however, we have assets dating back years from people who are likely unreachable. In fact we are currently in the process of trying to get all code contributors to sign our CLA, and even there with a bunch of follow up emails, we have not been able to reach everyone and may have to end up removing some work as a result. With the assets the problem is even harder as most of the time the artists doing the work aren’t available in git history (as they quite often weren’t the ones to commit to git), so we likely don’t even have a way to reliably get a list of people who need to sign. The only way to solve this would be to ask currently active artists which assets they made, and removing everything else. This is not a very good approach. So I guess as a result I’ll just mention the assets license in the game description, then. Thanks for the suggestion.