http://www.samba.plus/

Currently this, other than rolling your own, this appears the only way to have a Samba AD on Centos.

Later in the Samba 4.3 effort, MIT Kerberos is suppose to be supported so it MAY be easier to roll your own in a while, but until then, things are as they are.

I am rethinking my efforts to develop a ARM based AD. I may just fall back (as everyone else) to just an NT style PDC.