A quick note on Crunchy Bridge, it is pure Postgres, not "based" on Postgres. We haven't forked or modified code at all. And some of the above (Timescale) are extensions which do not change Postgres, but hook into the extension APIs.
Yes this is an important distinction between and extension for Postgres vs a fork of.
The short-sightedness of forking boggles my mind every time. Oh, you don't want a team of hundreds of literally the best Postgres programmers in the world working for you full time all the time for free? Ok dude, have fun with your fork.