Yes you can use unix base apps in mac os X. Mac os X is based off of bsd 4.5 and the update 10.2 is based off of bsd 5.0

Mac os x is in a nut shell is unix but with out bash you can use any unix apps in os X if you need gui apps goto www.apple.com goto the mac os x download place and get bash
or get X11 for os 10.2 that will let you run native true unix apps and linux apps in os X or you can run every thing from the shell or in X is called termial