It doesn’t make money, I was already hosting it for myself and decided to share the spare server capacity for good karma on the internet!

If it gets too expensive to run I’ll just block new people from signing up and only have existing users

This is really nice of you but if you want to serve the public it wouldn't hurt to think about how the service can be made self sufficient financially so that when you no longer wish to run it, or want to, it can be handed off to someone wants to do so, and without being a burden or needing more charity