On a technical level, no. You’re right. It would not be possible to capture the protocol entirely. But meta has serious cash to spend on marketing Threads. If they can capture enough of the ActivityPub market and were to collab with Bluesky and use their protocol (I forget the name), or make their own, it’s only a matter of time before the drop activitypub and force users either to join threads or lose access to their users.

Threads and Bluesky are kind of an existential threat to ActivityPub given Meta and Twitter’s track record with Open Graph, bootstrap, and public api’s.

Embrace, extend, extinguish.