Purpose of gems.rubyonrails.org

Is this gems repo supposed to be in sync with gems.rubyforge.org or is
the rubyonrails.org gem server a regular build of the HEAD Rails

For example, I noticed that actionmailer version 2.2.2 is different on
the 2 servers. The one on rubyonrails.org has a later version than
what was the actual 2.2.2 release.