Cpanel on FreeBSD 6.1-RELEASE

It may run on it, but as you've pointed out yourself it is not supported and you may not get any help from cPanel if you run into problems (despite what certain other people in these forums think):
http://www.cpanel.net/products/cPanelandWHM/linux/sys_requirements.htm

 

so far so good

I'm using freebsd 6.1 for production with cpanel, so far so good, just dont forget to search this forum to help you make tricky to make it runs, if you want jailshell and fpexec running dont forget to set kern_securelevel_enable="NO" on /etc/rc.conf

 

and the other thing is, when using GENERIC(default) kernel the cpanel runs with no problem at all, but when you recompile kernel with some options (quota,ipfilter,ipstealt,etc) and reboot the machine with the new kernel, the cpsrvd only running on port 2083 and 2087(actually not cpsrvd but stunnel) why this happen ? because cpsrvd still using 4x and 5x compat binary(CMIIW), so dont forget to add compat4x_enable="YES"
compat5x_enable="YES"

on your /etc/rc.conf and reboot the machine, after that freebsd 6.1 is ready to serve!