The real-time collaboration seems kind of cool but also makes me wonder how you handle history, permissions, etc. If I'm editing code and you're editing code and I hit 'RUN' I don't want your half finished code that doesn't compile to prevent me from running the game.
I'm curious why I'd choose this over say Unreal (free), Unity3D (free), Source 2 (free). ok, they aren't 100% free but they're effectively free until you make money.
They all have a track record of shipping games on multiple platforms (some more than others). Some already have huge communities. 2 of them export to HTML5 if that's what you want. They have large detail animation system, cutscene systems, visual programming system, shader editors, quality importers for tons of formats...