Unable to install nethforge repo

For some test i've install nethserver 6.5 on virtualbox. Everything works but i cannot install nethforge repositoy to install phpmyadmin.

 # yum install nethserver-nethforge-release
Loaded plugins: fastestmirror, nethserver_events
Loading mirror speeds from cached hostfile
Setting up Install Process
No package nethserver-nethforge-release available.
Error: Nothing to do

Any suggestion ?