The question here is how does it differ from the core concept of Open Source.
To which the answer is, it doesn't differ. But it automates it.
And this prompted me to another flight of fancy about the programmers' Cockaigne.
Even with something like Rails or TurboGears you still have to "manage" them in an old-fashioned way. You download the language, download the libraries, run scripts, find the newly generated files on your file system, open them and edit them in the editor etc. Once you are working on your application, managing it is your responsibility. If it's a web-app you have to worry about managing the web-server, making sure it finds the application, making sure the paths are right, the configuration info is right etc. etc.
Now imagine that you could develop an application on something like Ning : simply start by cloning an existing prototype, change only those bits that need changing, and then "compile" it (ie. export as a stand-alone package to the server of your choice) Even compile it down to run on clients like phones or set-top boxes.
I think we could be less than a decade away from a world where something like that is the norm. Where the current situation of programmers having to do their own sys-admin of their development environment, looks as outdated and inefficient as them having to do their own memory management using malloc and free.