The default RPMforge repository does not replace any CentOS base packages. In the past it used to, but those packages are now in a separate repository (rpmforge-extras) which is disabled by default.

You can find a complete listing of the RPMforge package packages at

via AdditionalResources/Repositories/RPMForge – CentOS Wiki.

The rpm at this link allows for yum to see the additional packages — such as alpine and perhaps others that were missing in the base.