I haven't actually even tested any environment yet, where i could develop same project with another person in realtime. SVN is 1 sort of choice but never tried installing its server part, and it's not realtime. Could share through google docs too i suppose, if i'd find a partner anyway. It would mean many of us forum-goers would propably have to team up, and that will cut amount of participant projects on already small forum.

But also making it group based challenge is silently hinting of wanting higher standard end results. Well, it will greatly depend on tools each groups have in their disposal. Single person can well do far superior projects if his tools and skills are that good. I'd also vote for allowing single-person submissions.