Since 389-ds-base is now in RHEL6 (as of RHEL6.1), we had to remove it
from EPEL6. We still want to make more recent/testing/experimental
versions available, though, so we are using
http://fedoraproject.org/wiki/Fedorapeople_Repos
for this purpose. In order to install the EPEL6 version, download
http://repos.fedorapeople.org/repos/rmeggins/389-ds-base/epel-389-ds-base...
and put it in the /etc/yum.repos.d directory. Then you should be able
to install 389-ds-base or 389-ds as any other EPEL package. See
http://directory.fedoraproject.org/wiki/Download#RHEL6.2FEPEL6 for more
information.