How is AppZero “OS-free application deployment”? Doesn’t the application require an OS?

We separate the application from the OS, packaging it into a single VAA/file for distribution – making it easy to copy and run at the destination machine.  However, when the VAA arrives at the destination server (physical or virtual) the application will require a working OS in order to run.  However, because the app can move among differently configured OSs in different environments, it can also easily move between Amazon and Rackspace without change.