Yesterday, Paul Ramsey from Refractions Research announced that GEOS project has moved to Subversion repository.
The new repository is available here through HTTP protocol. In order to checkout main development branch (trunk) of the GEOS sources, just run following command as anonymous user, without giving any username or password:
svn checkout http://svn.refractions.net/geos/trunk geos
All current commiters should be able to log in using their existing accounts and passwords.