I didn't immediately see a "fork" option (am I missing it?) - but I hope they add that feature. I think this has a ton of cool potential.

Open source design could be massive. There are already tons of places where designers give away assets to the community - fonts, PSD templates, logo templates, etc. But they all have the limitation of being done by a single designer. I think - despite the fears of "design by committee" that some might have - there could be some great stuff that comes out of collaborating in this way.