The moral imperative of a distributed social layer

Nostr does not use a blockchain (though you see a lot of lightning transactions, and theoretically could support any blockchain).

Relays on Nostr could then charge subscription fees or serve ads or otherwise select which content to include and exclude.

A protocol, like Nostr or Farcaster, can be permissionless and censorship resistant because there is no one to send a takedown request to in a distributed network.