But I strongly object to the tip amounts. Without going into too much detail, $0.25/week is not something I'd really consider a tip for a barista making my coffee, my dry cleaner, or any of the other myriad service folks I interact with on a regular basis. $0.25 will get you about 10 minutes of on-street parking in many cities; it might take longer to get your coffee. I'd guess that my attorney, physician, or my lawn guy would not consider $0.25/week a genuine "thank you" gesture as much as "hey, I have this quarter in my pocket." Personally, I think programmers are worth a lot more than most programmers think they themselves are worth.
Every other day, there's a HN post about some clueless business guy looking for technical co-founders. The HN community rages about how business people always undervalue their technical contributions. And then here's a project where programmers will tell you that a good project is worth $0.25/week. It that's true, maybe the "clueless" business guys are right to devalue technical work.
So while I really like your idea, I really do wish you'd reconsider the worth of programmers who contribute to these projects. I'm trying to be as constructive as possible here, because I think good things can come from what you're doing if you don't advance the notion that good programming in any meaningful quantity is worth $0.25.