This isn't meant to imply that Meta is, in this instance, offloading costs onto the community. But it's a tried-and-true tradition.
Log4j is the canonical example of this: it's such a boring piece of substrate that nobody noticed that it was effectively maintained by one person and had grown all kinds of configurable knobs and dials over the years.
Ultimately, I'm not saying that Meta is in the wrong here. But "here's a cash infusion with no long-term funding or staff commitment" is the kind of general mispattern that we're seeing w/r/t corporate open source.
no such thing
No, they don't deserve pennies. Facebook has given its code to the world - if anyone wants to keep that code maintained, then they can do so, but (I'd have thought needless to say) Facebook does not owe them a penny to maintain it just because they were kind enough to donate that version of their code. They can update it if they benefit from doing so.
Seriously, is this where we've got to? You can't open source your code unless you're able to pay for its maintenance in perpetuity? How is this in the spirit of openness? And, more to the point, how in the hell does this (incomprehensibly entitled) attitude encourage open source development?
Billionaire also donates million of dollars....
In any case, my point isn't really about whether they are being kind or not. That's a fortiori. It's that they certainly aren't under any obligation to provide it, nor to maintain it on account of having provided it.
(Although to respond to your precise point: I'm severely doubtful of your claim that Facebook gets 'huge marketing PR' from an open source library. No one is signing up to Facebook because of the [apparently-existent] 'huge marketing' of the fact that they wrote React.)