All the Qubes code is kept in GIT repositories. We divided the project into several components, each of which has its own separate repository, some of them:

• core-admin.git -- the core Qubes infrastructure responsible for VM management, VM templates, fs sharing, etc.
• gui-daemon.git -- GUI virtualization, Dom0 side.
• gui-agent-linux.git -- GUI virtualization, Linux VM side.
• linux-template-builder.git - scripts and other files used to create Qubes templates images.

You can browse the repositories ​on line via GitWeb. The Qubes official repositories are in the qubes-rX directory, where X is release number (1, 2, etc).

To clone a repository:

git clone git://git.qubes-os.org/qubes-r2/<repo_name>.git <repo_name>

e.g.:

git clone git://git.qubes-os.org/qubes-r2/core-admin.git core-admin

Currently the preferred way of contributing to the project is by sending a patch via the project's mailing list (git format-patch).