Depends what you mean by "Bluesky". Bluesky is a client, like Primal. There are a lot of other clients being built out on ATProtocol right now, like:
-WhiteWind (longform)
-Spark (TikTok)
-Flashes (Instagram/Olas)
-SmokeSignal (events)
-recipe.exchange (food)
-Tangled (github)
-Skeets (other Kind1)
-Deck.blue (notedeck)
...long list
I spend time over there too, and ATProtocol as a bare bones decentralised social protocol is very similar to Nostr. Nostr has a number of advantages depending on the use case (for B2B I think Nostr is much better) but lots of good architecture ideas on ATProtocol too.