What is Bazaar
http://bazaar-vcs.org/ bzr is another version control system, like Darcs, but is written in python. The main reason for the switch for mussa is that the darcs trac plugin broke because our darcs repository was too confusing.
You can down a version at http://bazaar-vcs.org/Download, if you have python with http://peak.telecommunity.com/DevCenter/EasyInstall EasyInstall setup, you can also install with easy_install bzr.
Checking out Mussa
Once you have bazaar available you can use the following to check out your own copy of the tree.
bzr branch http://mussa.caltech.edu/bzr/mussa