

Thats exactly what it sounds like, a “bridge”. An island doesnt stop being an island because it is connected to mainland with a bridge. You could also bridge twitter or facebook to mastodon, but that wouldnt make them part of the fediverse.
A bridge is just a piece of software that receives data from one protocol and re-formats it into another protocol. You could bridge SMS to bluesky if you wanted.
No, not really. It has already started caving to Turkish political censorship requests for example. They are implementing checkmark bullshit and from the start they required you to have an account to view all content.