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, !fedigrow@lemm.ee, 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.
It seems like you'd say that Matrix isn't included? It's not ActivityPub/AT/nostr
Matrix is not federated, it has nothing to do with the whole ActivityThing. They are two separate universes. Maybe there are bridges that I don't know of, but essentially they are not interconnected.
It's federated, just not to the ActivityPub universe, right? People have been able to join rooms on discuss.online using their matrix.org accounts, which to me counts as federated.
Matrix servers can talk to each other, so yes, they are federated. But Matrix is not ActivityPub.