Monday was a big day for Rackspace . The web host is one of the founders of OpenStack, an open cloud platform project that it collaborated on with NASA and a few others two years ago. Now, several releases and hundreds of additional contributors later, Rackspace has fired up its own commercial OpenStack cloud. This week U.S. customers gained access to the company’s OpenStack-backed Cloud Databases, Cloud Servers and a Control Panel. UK customers will get access later this month on the 15^th.

Rackspace began stress testing its OpenStack-based cloud back in April.  Although Dell, HP and several other companies are also rolling out OpenStack services, Rackspace’s is the largest. Before now, Rackspace’s cloud offerings used a proprietary technology. Existing customers won’t be forced to migrate away from the legacy services, but all new customers will use the OpenStack-based implementation.

OpenStack recently reached its second anniversary, and the open source effort has attracted a long list of major backers. However, cloud standards are far from mature. Multiple standards efforts are underway, and Amazon, the largest public cloud vendor, continues to invest in its proprietary platform. As more companies like Rackspace move to standards-based implementation it should become more difficult for vendors to justify stand-alone implementations.