Is it any service that includes the ability to federate? If so, are Matrix/XMPP/other non-ActivityPub services part of the Fediverse, or does Fediverse really just mean ActivityPub?
The context is wanting to promote a Matrix chat room on discuss.online: #online.discuss:discuss.online (see post). Does it belong in Lemmy communities like this one, [email protected], etc? Or does it not count as part of the Fediverse?
So, the term Fediverse basically refers to the ActivityPub protocol and the associated server software. Technically, it's not just ActivityPub, but also the AT protocol and nostr. Another layer to the Fediverse, at least in my mind, is having some federation. Meaning Bluesky isn't apart of the Fediverse, even though it's built on the AT Protocol, because of it's isolation. Since there's no interaction with Lemmy, Mastodon, PixelFed, or other federated social networks, it's not part of the Fediverse.
I think that ATP and nostr are sometimes included as part of the Fediverse because they both have bridges that allow connection. Without the bridges they're isolated.
XMPP also has a working ActivityPub bridge. But I think at some point these bridges are a bridge too far.
Software like Friendica or Hubzilla that can speak multiple protocols including AP are clearly part of the Fediverse, but things that need 3rd party bridges IMHO are not, as the creators clearly do no intend them to be part of it. Otherwise Xhitter would be also part of the Fediverse as bridges exist(ed in the past at least).
Wasn't the Twitter "bridge" just bot accounts though? It's a bit different with Bluesky because they've said that they completely support bridges between AT and AP but just don't have the resources to work on them themselves. Anyway, ActivityPub co-author Evan Prodromou gave an interview yesterday where he included Bluesky as part of the Fediverse because of the bridge.
Personally, I consider them to be both part of and not part of the Fediverse, I guess. I wouldn't send someone there and I also kind of think they're a bunch of dicks for re-inventing the wheel instead of contributing improvements here.