It's a good question, isn't it? Why does the Godot community (and not just OP) feel like they did "work for free". I've seldom come across this kind of sentiment elsewhere in opensource, so I am wondering why in this case there are mismatched expectations. Like I said, as an outsider I can't speak to any of this properly as I don't have more context. I am keeping an open mind either way, you may completely right in assuming that there were no promises made (legal or otherwise) that gave rise to this kind of expectation misalignment. The point I am making is this: regardless of the separation of Godot Foundation and W4, if the goodwill and work of the community was used to ensure some kind of future for W4, then it makes sense to pay that back in kind.
That's a good question. I'd assume "work for free" could be more accurately worded as "taken advantage of". After all, the vast majority of FOSS projects involve unpaid labor, and no one complains about "working for free" in FOSS.
What I mean is this: when a FOSS project is entirely community funded, one's hard work is just giving back to the community. But once a profit is made by the project, your hard work should now be compensated. Otherwise, you're being taken advantage of. For the forum OP, they're probably coming from the view of "why should Juan (and others) get paid for shipping half complete features when I'm not just paying out of pocket for the server everyone uses, but trying to help as best as I can (bug reports)?" After all, $8M for W4 is supposedly gone while Godot itself is in the negative every month? On the surface, that looks sketchy.
There is a bit of entitlement in such a thought, I'd argue, but it's not completely unjustified.
For another example, Linux's and Blender's main developers get paid, but they're the exception to the rule. Any community involvement in the form of patches and bug reports are all unpaid. But people don't complain about that because the Linux Foundation and the Blender Foundation are both non-profits. W4, however, is a for-profit. So, millions are going to a for-profit organization while the people working on the non-profit side languish.
