Second this. I'm fond of just enough principle, and this is exactly that.

Or better this: https://github.com/basecamp/once-campfire

I'm confused. In the FAQ they mention issuing licenses for self-hosting, but the code base in MIT licensed so why would you need an issued license?

I am somewhat guessing here: They used to sell this app (for, idk, $300 I think?) until recently. The FAQ might not have been updated in full to reflect the fact that it's now open source.