itch.io

This is drifting off topic, but I feel this is rather important to point out : that's not what "royalty" means. A royalty is a payment for continuous use of something. It is not payment for initial access or initial modification of the thing. That's why they tend to be percentages of the profit of a larger commercial work. GPL allows charges for modification and distribution but it definitely doesn't allow charging for the actual use of it.

Also to clarify since I'm replying anyway, I meant that implication in context. It is completely pointless to require payment to digitally access a GPL work, since the person then can just release the work for free themselves. The reasons one would want to require payment for access are either because a physical copy always costs money somehow to create or as a symbolic way to charge for the service to the community at large, neither of which apply here.