Good for you. I see UNIX as being a nice little trademark. SVRx vs BSD-style is just a different polarisation.
Pretty disappointing article. I would have expected more from a Computing Senior. If I were grading this I'd give it an "R" for "Resubmit".
First you should tell us what a UNIX is. A UNIX is not X11 - don't you have GNU/Linux boxes without X11? Do they respond on port 6000 if XFree86 is not installed? A quick grep of Mac OS X's /etc/services file brings out the following:
#x11 6000-6063/tcp X Window System
#x11 6000-6063/udp X Window System
so Mac OS X knows about X11 certainly.
A UNIX doesn't need to contain any GNU code (because GNU's Not Unix) and fortune...is just a toy. Now, perhaps those were badly chosen examples but it would better to resubmit with some better chosen ones.
According to the Open Group. UNIX is "specification, product, trademark and technology." You'll also notice that GNU/Linux distributions meet those criteria as much as Mac OS X so whether OSX is a "better" UNIX than GNU/Linux is not the argument. When submitting an essay, always check whether you are actually answering the question. Your "defenses" of GNU/linux appear as just that - defensive. You've got to ask yourself why?
The best argument you provided was the one about NetInfo and pro-flat files and "/etc". Please research WHY the configuration files are in /etc and also provide a reason why NIS/yp networks and others with a distributed logon system might not be UNIX. The problem here is that you tell us that flat files == UNIX when this simply isn't the case. There's an inference that NetInfo is bad but no evidence to support it.
Finally, a personal comment on the theme. People who use GNU/Linux should not be rounding on those who are using other UNIX-based or UNIX-like systems. Whether or not it will consign Apple to it's apparently deserved oblivion is not for mere speculation but rather a proper subject to be examined and if Mac OS X does indeed fail, then what does that say about UNIX-like systems. How does it benefit the GNU/Linux users? I personally believe that 5 million users of Mac OS X are a benefit to the "unix" community as some of them will bring knowledge and experience that could be valuable. For those of you who develop software for a living, this provides an easy way to get software ported to 5 million more desktops rather than the pain of porting from GNU/Linux to Windows.
My personal view is that if I can migrate people off the administrative nightmare that is Windows, any target will do - even those non-standard UNIX "flavours" like GNU/Linux and Mac OS X.