This is pretty neat in a weird sort of way. Craftyy is a web-based experiment in building a crowdsource friendly environment for game development. Here, you'll be able to iterate upon an idea (or come up with one of your own) and add your own flavor to it. From there, others can further expand your concepts and so on. Should Craftyy get fully funded, it looks like the developers will make the game free to play. There are also apparently plans for making the source code accessible sometime in the future.

Those interested in assisting the funding of the project should head here. As for everyone else, you can check out the beta version here.