Apache CloudStack started as a project called VMOPs in 2008, was later open sourced as CloudStack and acquired by Citrix in 2011. In 2012 it was relicensed under the Apache License Version 2 and accepted as an Apache incubating project. CloudStack is a fully open source and community driven project for building IaaS clouds. It supports various cloud standards like OCCI for infrastructure management and OpenFlow for software defined networking. The first Apache CloudStack 4.0 release is expected in September 2012.