It's trivial for any Tom, Dick and Harry to fork an opensource project and "extend" it - but none have so far actually extended the engine - have they implemented any new W3C standards or fixed any compliance bugs? Have they made any improvements to the rendering engine? I'm not aware of any of the forks doing anything significant, besides just superficial UI features and preventing merging certain pieces of code (like Manifest V3). If any of the forks have deviated in any significant way (like how Blink deviated from Webkit), please do enlighten me, because otherwise they're just copies dependent largely on Google for all the core improvements.
More than half of the committers on Chromium aren't Google employees. I assume the reason they haven't gone off and forked it is because they have no reason to.
They probably haven't forked it because they know it's a futile effort to maintain and develop something as complex as Blink. Anyone who's ever worked on a large project like that knows very well it's easier to start from scratch, even if it's going to take a herculean effort.
