Google is still very committed to providing a great place to host open source projects at http://code.google.com/hosting, that has not changed. But many of us are also fans of GitHub, and recognize that there is a great community of developers there (particularly in the ruby community).

The Google account on GitHub has been setup simply as a place where some open source Google projects can be mirrored. As another commenter noted, this is actually one of the points of a DVCS.