The Gu has the details.

The Entity Framework source code is today being released under an open source license (Apache 2.0), and the code repository is now hosted on CodePlex (using Git) to further increase development transparency. This will enable everyone in the community to be able to engage and provide feedback on code checkins, bug fixes, new feature development and build and test the product on a daily basis using the most up to date version of the source code and tests. Community contributions will also be welcomed, so you can help shape and build Entity Framework into an even better product. You can find all the details on the Entity Framework CodePlex Site.