At the heart of this - if you consider it generously - is a principle that we can possibly all sign up to, namely that "large commercial entities" should (should from a moral, not legal standpoint) "pay back" to the open source software that makes them money.
The principle however has been totally undermined by MM's actions, which have been completely out of line. His behaviour has been abhorrent. I've been shocked (possibly naively) that a single individual could have such huge power over an open source project that they could literally turn it off (referring here to the update mechanism that WPEngine was using).
I've been even more shocked and appalled by this plugin takeover. ACF is a central piece of pretty much all WP developers' / agencies toolkit. Those of us who have been in this game a long time remember WP before it, and the breath of fresh air that it was to finally be able to define complex relationships between posts and provide our users with a GUI that actually worked well for complicated sites. ACF have pushed and supported this technology for years and years - firstly under the expertise of Elliot Condon, now under the aegis of WPEngine. I know some of the developer team at ACF personally - they're excellent people, making brilliant code, and most of them are putting huge efforts into WP as an open source project even aside from their efforts in maintaining and extending ACF.
The forking of a plugin is one thing. A fair way to do this would be to fork it, and start from zero installs. Automattic could have done that, promoted the hell out of "SCF" and got users in a way that was at least slightly (?) fair.
Simply switching the name and keeping the slug - and thus the 2+million sites - should be thought of as theft. It's outrageous, it's totally petty, and I so far haven't seen a single person being supportive of this (probably?) unilateral action by one - apparently increasingly unhinged - individual.
The wider problem of course is the effect this has on the vibrant WP ecosystem which as someone else in this thread has pointed out is a critical (erstwhile) open cornerstone of the web.
I am still hoping that this will subside into history and it'll all sort but it has left me and many WP devs I know with a pretty bitter taste.