San Francisco-based Nimbula, a firm started by former ex-Amazon EC2 execs, said today that it has launched a new, cloud computing operating system startup. Nimbula said it is looking to provide a "comprehensive" cloud computing operating system, to be launched sometime in the fall. The firm was co-founded by Chris Pinkham and Willem van Biljon, both of whom helped develop Amazon EC2. Nimbula and its execs are originally from South Africa, where the firm continues to have operations. Nimbula is venture backed by Sequoia Capital and VMware, and counts Sequoia's Roelof Botha and VMware foudner Diane Greene as board members.