Passion. I work constantly on my side projects, and would gladly have helped the devs. I've asked them 3 times - roughly once a year. I've got the same response each time, but I don't look at it as begging, just as reminding them I'd help. Completely for nothing besides my satisfaction of helping.
Programming, and racing (okay- sim racing), are my primary interests and hobbies. Although I do have a few others, but those take a back burner to these two.