Take a look at the instructions for getting the Mac OSX nameserver going. Its essentially the same as for Linux or BSD, except for the part where you also get to edit, by hand in a text editor, the system of the Mac too.
I got it going and it appears to work correctly; it looks stuff up when I set nslookup to localhost, without hitting the DNS in the router. I don't want it running as a forwarding-only type, because I kind of want to add creative DNS records for domains that contain nothing but crap anyways (doubleclick comes to mind) and then have the router use the Mac as its nameserver.
Yes, I shall bring PRAVDA to "free internet" for local masses! Muahahahah!
I am about to activate the nameserver! Wish me luck, for if this fails badly, I may never be able to post again.