For sure, but the membership fees these companies pay are really quite small (bottom of this page https://www.eclipse.org/membership/prospectus/), and they mainly go towards infrastructure, running the working groups, and conferences. The projects get some benefits, but they don't get a lot of full time developers (in fact, I'd be surprised if they get even a fraction of 1 FTE), and are largely run either by volunteers or by people doing this in their 20% time in regular day jobs.
In any case, Cursor didn't pay any money here, so they get to keep all the pieces when the code they used for free breaks.
(And a fun but irrelevant bonus fact: Eclipse was originally made by IBM)