The problem is that the tens of thousands of small businesses who placed their trust in Wordpress will be damaged by this. I know - anecdotally - that many of those people like Wordpress “because it is free” (like both beer and speech) and because they know - even fuzzily - that because of that there’s lots of cool useful stuff that is available.
Now, sure, a lot of that cool useful stuff will still work with a fork. But it splits the message and gradually - not overnight - people developing that cool and useful stuff may lose faith and do something else.
What Millenweg is doing hits at the very heart of what open source means - and what community means - and is, as far as I can see, an absolutely cynical move made in the pursuit of profit and vanity.