NASA and its Eucalyptus-based Nebula

Here I leave an article from The Register about NASA's Nebula infrastructure cloud. If you don't know yet how NASA's project relates to this blog, read the following paragraph which I quote from the article (Bold font added for emphasis).

"You can think of Nebula as a version of Amazon's Elastic Compute Cloud (EC2) and Simple Storage Service (S3) that's used only within the federal government, a service that provides on-demand access to scalable processing and storage resources. It's based on Eucalyptus, the open source cloud platform that's bundled with the latest version of Ubuntu. Eucalyptus. Karmic Koala. You get the picture."

I cannot but wonder why NASA chose Eucalyptus to build Nebula...