Mezzanine is a simple yet powerful BSD licensed CMS for building Django powered sites. It just reached version 1.0 after 2 years in development with contributions from dozens of developers in its community of hundreds.
As part of the 1.0 release, and new homepage for the project was designed by members of the community. It uses Bootstrap 2.0 and is fully responsive. Mezzanine itself also uses a responsive Bootstrap 2.0 and most of its features, for the default templates that come with the project. Check out the demo site which also includes a Bootswatch theme switcher, featuring a dozen different Bootstrap themes.