If the money isn't the motivator (gets donated anyway) you could use a virtual currency. "karma" or something similar. You might monitor svn/git activity and cr

If the money isn't the motivator (gets donated anyway) you could use a virtual currency. "karma" or something similar. You might monitor svn/git activity and create a community where people could rate each others commits and give each other some "karma" that way (hacker news with code submits instead of news, sort of).