Let's answer two ways that could be taken... No, I didn't mean Mac OS X is 40, my grammar radar missed that possible interpretation. (Though being a hereditary Unix through NeXT, BSD4.4 and back, it could be considered such)
By any measure I have seen in the past 5 years, Mac OS X continually shows market penetration 5-8+ times that of Linux, compared to which any other Unix system usage can mostly be considered statistical noise.
That's not to say they don't have relevance or followers, but when it comes to getting the average user putting their hands on a Unix or Unix-like system, no other compares to Mac OS X, and that's not even counting embedded usage like the iPhone and iPod Touch.
When I started doing Unix Admin professionally Unix was just turning 30, Linux was poised to take over the Desktop, Mac OS X was just a glimmer of hope, and Sun was the king of commercial Unix.
When I started using Minix, Unix was only 20, but RMS was kvetching about source code (and Hurd was Coming Soon), BSD had just won it's freedom, and Steve Jobs was doing cool things over at NeXT. Unix was just leaving it's First "Golden Age"...
Now, at 40, Mac OS X is the most used Unix system, Sun was just bought cheap, most other commercial Unix systems are defunct... But with Android, Pre, and iPhone all putting *nix systems in the palms of millions, Macs selling more than ever, and many companies offering Linux pre-installed in the box, Unix is as relevant as ever.
I've noticed several design suggestions in your code.