As others have said, it isn't hard at all. It's just Git. You can host your Git projects anywhere you want. To be fair, Github has reasonable prices and even though I complain about the strange UI, there is a lot of good functionality. The strangely named "Network Graph" has saved my butt more than once.

I have been thinking, though, that I don't like the workflow associated with commenting out of band. I would really prefer that people comment by making a branch and modifying my PR (either with code comments or just fixing the problems directly). If I knew how to do that efficiently, I probably would have almost no attachment left to GH.

It's actually simple. GitHub tests on their free users and see their reaction. If the feedback is positive, move it to paid clients. If not, keep frustrating your free clients so they move to paid accounts.