While Amazon has not released many details of the software that powers its cloud services, the company to Eucalyptus, another open-source cloud project that replicates the APIs (Application Programming Interfaces) of Amazon Web Services. The idea behind Eucalyptus is that users of AWS could build their own internal clouds with Eucalyptus and move workloads between Amazon's cloud and their own.

Simply replicating the API, however, is not sufficient, Moorman argued. "The problem is the APIs are really just an interface to the real technology. Amazon's [Simple Storage Service] and [Elastic Cloud Compute] are complicated technologies. In order to replicate a world-class cloud, you really have to have the code end-to-end," Moorman said. "People want to think of the cloud as a protocol, but it is a whole technology stack."

"When you're cloning something, you are always playing catch-up. So it is not even a question of technical merit. Though I'm not sure reverse engineering all of Amazon's work is even possible," Moorman said. As an example, he pointed to Eucalyptus' Walrus feature, which replicated Amazon's S3 (Simple Storage Service). Walrus "behaves differently than S3 and scales differently than S3," Moorman said. (Eucalyptus did not respond to inquiries for a response.)

Amazon to be the largest provider of cloud services. It recently announced that users more than a trillion objects in its Simple Storage Service (S3).

Launched in 2006, Amazon Web Services provides computing nodes, databases, storage, load balancing and other services, all available on pay-as-you-go pricing plans. It is increasingly being used by large-scale Web service providers such as .