I, personally, am optimistic that we'll be able to do it for the core at some point. Something not mentioned in the original article is that architecturally our VMM allows us to easily change the set of available functionality (virtual devices, backing implementations of those, etc.). So, for example, the fuzzing Andy described as depending on our custom VMM isn't even linked into the VMM run in GCE, nor are custom devices we keep around for testing and development. I'd very much like it if we could layer the VMM in such a way that we could release a useful core that forms the basis of the VMM we consume internally. Today, though, the layering just isn't quite there (among other technical and business reasons, as Andy says), and there are Googley specifics in places that would make even the VMM core (minus devices, etc.) unviable outside of Google.