All the Qubes code is kept in GIT repositories. We divided the project into several components, each of which has its own separate repository:
-`core.git` -- the core Qubes infrastructure responsible for VM management, VM temaplates, fs sharing, etc.
-`gui.git` -- GUI virtualization, both Dom0 and VM side.
-`template-builder.git` - scripts and other files used to create Qubes templates and NetVM images.
You can browse the repositories [on line via GitWeb](http://gitweb.qubes-os.org/gitweb/). The Qubes official repositories are in the `mainstream` directory.