The important take away here is that the protocol is not what's important about the fediverse. Bluesky itself could release first class support for ActivityPub tomorrow. There are many other servers already out there that speak ActivityPub but are *not* mastodon servers. Mastodon could also change it's tech so that it will only communicate with other servers who are "real mastodon". But that would be silly. No one is in control of the fediverse. By design.