Tootfinder

I'm asking for help conceptualising & understanding and (on this rare occasion) I'll accept long/slightly mansplain-y answers:
As I currently understand it, #BlueSky is structured a bit like the FediVerse, but uses the #ATprotocol not ActivityPub.
Most people are on bsky.social, but you don't have to be. How are the non-bsky.social 'instances' run? Where are the Ts&Cs for federating? Is it possible to sidestep BlueSky Moderation policies by joining a different 'instance'? Is that partly what #BlackSky is?