OS X & Unix software compatibility?

Well still reading about OS X after about 2 wks w/ my new rMBP (and about to obtain our new iMac) - NOW, reading the book shown below & trying to reacquaint myself w/ the UNIX based OS (had Ubuntu on an old IBM laptop a few years back) - now having used a lot of this Linux based software on the old laptop, will these programs run natively on Mountain Lion? If so, any links to places showing some of the offerings to consider? Thanks for any comments and links - Dave

Most people who want to run familiar linux apps use "repositories" - package manager software, the packages having been re-compiled for OS X. Choose from Fink, MacPorts and Homebrew. I don't know which is best.

read here:
What are pros and cons for MacPorts, Fink and Homebrew? - Ask Different