I guarantee they got all kinds of hate and weirdness sent their way, too. Any game with a notable userbase does, including the commercial ones. Like,
weird, personal, abusive shit from people who demonstrably (it's pretty clear from their "ideas") have no idea what they're talking about and evidently have unfortunate (for everyone else, anyway) amounts of free time on their hands.
And I don't just mean "you monetized this in a way I dislike" or "boo, DRM" or "you had dozens of game-breaking bugs at launch" or whatever, which, maybe don't be a dick about it, but at least I get why those things upset people and, especially in the last case, why they might get a bit entitled-seeming about it, since they did part with money—no, it's over the tiniest, most trivial stuff, including, often, things that are the way they are for a very good reason and would piss off 100x as many people if the abusive jerk got his (or her, I guess... but realistically, it's just about always a "his") way. But no, this minor thing is wrong so you're incompetent and any idiot could do better and [some names they somehow came up with, sometimes with disturbing accuracy] who worked on that part should be fired immediately. JFC. They'll spam you with this crap, on every channel they can.
And that's if you're not a woman prominent in the project. Then you get the creeper shit, too.
There's no possible way the DF devs haven't seen their fair share of that.
(though, sure, they were ultimately able to monetize it in a way that very few passion projects of that sort ever can, and certainly not utility open source libraries—that part of the story's way different)