there are also a bunch of other apps using atproto that are completely independent ex: @tangled.sh (github) @bad-example.com has run their own infra to make bsky post w/o any bsky infra and developed a lot of tools for self hosting pieces with @microcosm.blue like constellation.microcosm.blue
@rudyfraser.com has demonstrated the porting of over 400 accounts from the Bluesky personal data servers (PDS where your account data lives) to his own infra, you can check the accounts here pdsls.dev/blacksky.app. This is non-trivial at the current moment on AP and this includes follow data etc.
The blacksky project is independently funded and runs their own separate moderation service (atproto is designed for pluggable moderation) and relay atproto.africa and client blacksky.community they even run their own implementation for the entire stack.