Yesterday Red Hat announced at the Open Cloud Conference in Sunnyvale, CA, the release of OpenShift as open source, and the ability to take OpenShift and use it to run your own PaaS.
What does this mean? Firstly, you can take the source for OpenShift and view or modify it (under the Apache 2 license) as you please. Secondly, if you have a need to run your systems using a private cloud model locally or hosted using your own hosting provider, you can take OpenShift and deploy it where ever you need, and still take advantage of the ability to dynamically provision/deploy apps and services using the OpenShift toolset.
This is very similar to the approach VMWare have taken with Micro Cloud Foundry, which is also open source, and also available so you can run the PaaS yourself.