I'd personally be very happy if Threads gives up control over their users but it remains to be seen. ActivityPub also lacks the very strong account portability feature that made AT Protocol necessary.
AT Protocol is completely open source and the Bluesky network is completely open. The Bluesky network has had an open API for a year with full access to all public data (no auth required):
websocat wss://bsky.network/xrpc/com.atproto.sync.subscribeRepos
More info on: https://atproto.com