I'm sure people who develop it doesn't want money and fame, but they're just doing what they like. However, curl has commercial support contracts if you need.
> Sounds like a thankless job to fix obscure worstfit bugs.
It may look thankless, but it's not. curl is critical infrastructure at this point. While https://xkcd.com/2347/ applies squarely to cURL, it's actually nice that the lead developer is making some money out of his endeavor.
They fix bugs because they simply want their product to be better, if if I were to take a guess? Like, I'm sure curl's contributors worked on OS-specific problems before, and it wouldn't be the last.
> to fix obscure worstfit bugs.
Again my premise is "if there are actually common problems caused by it". This specific bug does sound like that, at least not for now.