OpenStack’s proposition is simple, with the same freely downloadable code powering big commercial cloud data centers run by Rackspace, Hewlett Packard, and others. Customers, the argument goes, are therefore able to easily move their applications from one provider to another without having to alter their own programs. They can even download a copy of OpenStack to run inside their own data center as well, which (in principle) makes it feasible to move computing jobs from a private data center to commercial clouds and back again, at will.