> A complex multi-million line project representing 1000s of manyears of work, essentially needs dedicated full-time highly skilled engineers to be forked.
WebKit, from which Google Blink was forked includes dedicated, full-time, highly-skilled engineers from Apple and elsewhere that could incorporate material from Blink -- as well as all the other browser projects which might want to use material from WebKit (pre- or post-fork) or Blink; so the situation with regard to "open source"-ness is the same as it was before the fork, even with this "it needs full-time highly-skilled engineers" to use it proviso.
> Highly complex codebases seldom progress much as community projects after the original company has abandoned the paid contributors
Which is one of the reasons that forks between projects where both sides of the fork are paying contributors and the fork results in both sides being able to streamline and more efficiently return value to their sponsors (thus, making the sponsorship from both the prime sponsor of the original project and the sponsor that used to pay people to work on that project but which is now sponsoring their own fork more likely to continue) is good, as it puts each post-fork project on a more secure footing than the pre-fork project was.
WebKit, from which Google Blink was forked includes dedicated, full-time, highly-skilled engineers from Apple and elsewhere that could incorporate material from Blink -- as well as all the other browser projects which might want to use material from WebKit (pre- or post-fork) or Blink; so the situation with regard to "open source"-ness is the same as it was before the fork, even with this "it needs full-time highly-skilled engineers" to use it proviso.
> Highly complex codebases seldom progress much as community projects after the original company has abandoned the paid contributors
Which is one of the reasons that forks between projects where both sides of the fork are paying contributors and the fork results in both sides being able to streamline and more efficiently return value to their sponsors (thus, making the sponsorship from both the prime sponsor of the original project and the sponsor that used to pay people to work on that project but which is now sponsoring their own fork more likely to continue) is good, as it puts each post-fork project on a more secure footing than the pre-fork project was.