It is now. There were a few years where it had basically disappeared (2015-2018). When Apple eventually put it back in the open-source world, it was done with little fanfare so it could be easy to miss.

same guy who wrote mvsqlite btw

Really, what is the reason why?

Apple acquired the company in 2015 and 3 years later open-sourced the database.

(so much misinformation in this thread, this isn't hard to check)