RepoForge might be outdated. We have no updates since very long time.
It says on the site, and connecting to the packages seems to take forever, maybe RPM Fusion or Remi's repo are interesting alternatives. Although RPM Fusion doesn't seem to have EL7 packages, yet?.
But I think it would be good to keep the example.
Ps https://wiki.centos.org/AdditionalResources/Repositories/ also marks RepoForge as dead, do not use