Thanks to the Engineering Walden, you can now get CentOS 6 set up in a FreeBSD 10.2 jail. Follow the link for the full tutorial.

CentOS 6!  In a jail on the FreeBSD 10.2 kernel!  THAT’S EFFING AWESOME.

I just got this up and running after some hours spent cobbling together instructions from the various sources to which I link below, and then troubleshooting some issues (one of which is listed at the bottom for anyone else who encounters it), but it works.

Link: The Midnight Oil: Jailing CentOS 6 in FreeBSD 10.2 Edition