BuddyPress was the first plugin developed for WP. ClassicPress without CalssicBuddyPress is like Stalio without Olio.
If any developers want to fork BuddyPress, they’re welcome to do so.
BuddyPress is a very odd plugin. It completely hijacks the site instead of doing things “the WordPress way”. These days it’s really intended primarily for wordpress.org.
It’s actually pretty easy to build a forum on CP/WP using regular posts, categories, and comments (and a CPT, if desired). I wouldn’t recommend anyone fork BuddyPress for CP.