ASP.NET vNext (and Rosyln) runs on Mono, on both Mac and Linux today. While Mono isn't a project from Microsoft, we'll collaborate with the Mono team, plus Mono will be added to our test matrix. It's our aspiration that it «just work.»
ASP.NET vNext will let you deploy your own version of the .NET Framework on an app-by-app-basis.
There’s no assemblies in there because the assemblies never exist on the disk. It’s actually faster and easier to have the compiler do all the work in memory. This way you don’t have to read source, write out dlls, then read the dlls in again.