I was writing an even longer post but hit the back key on my keyboard and lost everything... yay.
Not hating on Macs.. both my brothers use them everyday (macbook and iMac) unless they want to play one of their games or run some .exe.. then they go sit at the PC desktop.
It would take a very motivated developer months to get DP to even compile on OS X. And if they're not jitspoe, they can't even play the game because they would need the closed-source gamex86.dll code that only jitspoe has.
Glad you mentioned Linux, that client barely works (and for some it just plain won't) and jitspoe doesn't spend any time on it unless the same bug is in the dedicated server.
I watched some really smart developers work on porting early releases of warsow to Mac. There were lots of sound problems, lots of mouse input problems, timing was off with the win/linux servers so you chopped all over the place and had a ton of prediction errors, textures randomly not working, maps not loading... and that was based off the Linux client code that was pretty solid. I don't know much about their 0.5 Mac client, except there aren't as many complaints so someone must have worked extremely hard in the last 2 yrs to fix most those problems.