Adam Mosseri:
Second, threads posted by me and a few members of the Threads team will be available on other fediverse platforms like Mastodon starting this week. This test is a small but meaningful step towards making Threads interoperable with other apps using ActivityPub — we’re committed to doing this so that people can find community and engage with the content most relevant to them, no matter what app they use.
Absolutely not, federating with Threads is the first step in the Embrace, Extend, Extinguish process that businesses have used in the past to kill things like the fediverse. This is a win for businesses that want to see the fediverse dead and buried