Basically the person has subversion setup on their server. It allows multiple people to access a project for instance on the same server using login credentials to access specified files. Exploitation would depend really on whether there is any exploits about for this type attack or bruteforcing. Needless to say if you get the login credentials you will have to subvert any restrictions on the SVN user.
"If you want to create a project or a set of files that multiple people need to have access to (and potentially edit), you can use Subversion..."
User restrictions are usually in "/etc/svn-access.conf" I believe.