I'm a member at a freelancer cooperative and we offer some paid open-source products. The model we have is free for communities, paid for business. There is just one license and you always need a license key. But you can get a free one as a community user:
Well, just sharing our approach. What I believe would be important in general is finding a solution that promotes community contribution. You'll want to build a vibrant community around the product. Restricting size or customization options could work against that.
This would be really beneficial for my use case to be honest: Building a hobby community.