It's an interesting idea and I don't mean to impede creativity, but I would worry that it'd become a distraction. And for some, even a goal in itself to simply earn "points" endlessly for "that big project" (which may never start) rather than encourage a less formal cooperative online community. The "reputation" thing here is more than enough "score-keeping" for me personally. The Wiki article warns about overhead/cost of keeping it running, and that's another thing that makes me hesitant.
If all you want to do is encourage development projects, I put an alternate type of suggestion (less "gamey", no pun intended, and more "gamedev") I dubbed a "team-building/matchmaking" service, similar to the old neverwinterconnections.com site. (That site was used to match up various Neverwinter Nights players and GMs with similar interests and play styles to allow groups of people to form small gaming circles.) If it's modeled after the NWC system, that moves some "overhead" to the community sort of like a rating or online review website. (Ex. If a ranking system is needed, use a rating system like "Would you work with this person again?", "This person was particularly creative.", "This developer was dedicated and motivated." etc.)
I tried to describe it loosely here, for what it's worth: