laconica/statusnet implemented federation, and identi.ca was the largest node of the federated network back then.

identi.ca moved to the pump.io protocol few years later, but statusnet lived on, later becoming GNU social. GNU social nodes were largely cut off when the then-already-dominant Mastodon broke compatibility with the statusnet protocol before GNU social had a working implementation of ActivityPub. now it does, but even when it didn't, it never ceased to be part of the fediverse, that encompasses more than activitypub