I don't sorry, I forgot about this when I heard about the possible problems of compatability with TV tuner cards in FreeBSD..
..unless you got some cards to work on FreeNAS?
Here are the builds for freeBSD located: http://www.satlover.eu/forum/oscam-downloads/40915-oscam-for-freebsd.html
In regards to installing it, I'm afraid I can't help you.. just google it, and with some thinkering i'm sure you'll get to figure it out. (And maybe post a tutorial about it afterwards?)