Website's download page https://gnu.io/social/resources/code/ contains the following git clone code: git clone git://gitorious.org/social/mainline.git. But trying it out leads to:
% git clone git://gitorious.org/social/mainline.git
Cloning into 'mainline'...
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.