Is OS X Unix?
Many points in the article are valid, but the case of 'OS X not being Unix' is weak. For example:
JPR: "Further, show me a Linux distribution that ignores /etc and stores its configuration data in a binary registry. "
JPR: "...gcc, gdb, X, and all those other utilities (even fortune) that make Unix Unix"
Commercial Unix vendors continuously change they policies of "bundling" (or not) development tools and such. When I worked with Solaris and AIX cc was an at-cost option. When I worked with (late and lamented) Interactive even TCP/IP was at-cost option!
So, is OS X Unix? It is. Is it viable drop-in replacement for Linux, Solaris, AIX workstation? I'll agree with JPR: probably not.