The svn repository has been migrated to at git repository hosted on https://github.com/Gecode/gecode where all GitHub services are supported (issue tracking, pull request, automatic builds via Travis, …).
The now defunct Gmane archive of the old users mailing list has been replaced by an archive hosted one Gecode's webpages at https://gecode.github.io/users-archive/. It is not pretty but still useful.