Tell HN: Startup Idea - Github + Heroku for Open Source Webapps

I just had an idea while reading praise of GitHub - how cool would it be if you could launch a web app on a free hosting service like Heroku, and then keep the code base totally open source and free to commit to? Bugs could be fixed by the community, and new features could be added? It would be like a combination between the free Heroku offering and GitHub - perhaps even these two companies should build it!

I think it's the kind of idea that sounds like it would be hindered by being publicly editable, but would work great in practice (think Wikipedia). It would be perfect for someone who has an idea for a simple side project web app, throws together a quick prototype, and doesn't have the time to finish it.

What do you guys think?