So run a local server and turn federation off. Like you can run a private e-mail server. Why not use and contribute to the common protocol that does allow federation? I see no point for a FOSS project in proliferating non federated IM protocols, and wasting resources on that, while federated ones still didn't even reach wide adoption.
I view it the opposite way. It's waste of time to reinvent the wheel and not concentrate resources. Federated protocol can be used without federation fine, but not the other way around. For FOSS projects, not doing it is strange, especially when lack of adoption for federated options is still a major global problem.
So I'd question the intent behind this particular project. For those who don't care about openness (like Slack), I'd expect such behavior. But for open projects - not really.
