Ironically dotCloud started out in 2008 as a very similar project, with the same lofty goals. We had VM templating and versioning (
https://github.com/dotcloud/cloudlets), cross-infrastructure deployment (
https://bitbucket.org/dotcloud/vm2vm), various goodies based on container virtualization, copy-on-write filesystems (
https://github.com/dotcloud/aufs.py), and an orchestration layer to tie it all together (I found an old fork at
https://bitbucket.org/Foi3GraS/dotcloud). It powered various 3d-party "XaaS" throughout 2009 - here's a French provider that still seems to be alive:
http://www.diva-cloud.com/softwaresThen in 2010 we joined YC, and actually tested our claim that "you can make it publicly available as a service!". Within 6 months we had rewritten 100% of the codebase around the real constraints of deploying and being responsible for tens of thousands of applications. We are only now getting around to open-sourcing some of these new, battle-tested components: a great example is ZeroRPC (http://github.com/dotcloud/zerorpc-python). More to come.
My hard-earned advice to you Justin is: you have to operate PlatformLayer as a service first and foremost, and the code you publish must flow from the real-world experience of operating that service, charging money for it, and being accountable for its reliability - not the other way around. There's a reason VMWare is a flop in the cloud world: they don't know how to operate their stuff.
In any case, I'm super excited to see so much open-source activity around solving these problems. Back in 2008 it was quite lonely :)
We hackers all benefit from this friendly competition in the end - happy hacking!