Have they open sourced the server? Revival projects should always do this, otherwise they are preserving nothing. A single point of failure means someone else will have to reverse-engineer the protocol and write the server software again in the future. Do it for posterity!

I'm unable to find the server, but it looks like they've released some protocol analysis tooling: https://github.com/iconidentify/wiretap

Why wouldn't a project like this be OSS? How do they expect to monetize? People buying dialtone subscriptions as a social network?