The Open Cloud Manifesto proposes the idea of an open cloud mainly for portability/flexibility in choosing cloud provider and efficiency (developers used to the API, maturing code, etc).
Unfortunately, the paper is written from a cloud user standpoint. From a business perspective, the leader cloud providers have no incentives to open up their interfaces. The tradition of successful IT business seems more to indicate to rely on very closed systems e.g. look at Microsoft, Google (even though appears open it is actually very closed).
In fact, this is the approach for cloud that Google is pursuing with Google Apps. AppDrop could turn out to be a bad replica of the original due to many reasons and unknown tweaks/details of the Google setup.