Several readers took me to task for referring to Linux, BSD, and OS X as Unix. Lighten up, folks -- I'm on your side. No one feels more protective of Unix's heritage than I. Unix has a rich legacy that deserves to be preserved and accurately conveyed to new generations of computer scientists. It rattles many of us to see that the operating systems that best exemplify Unix traditions today aren't Unix at all.
Unix no longer describes a particular product or collection of software. It's not even a trademark in the real sense -- do you even know who owns the word now? Nobody cares. For the record, the Unix trademark is owned by The Open Group (opengroup.org). Few in IT get worked up over whether an operating system is genuine Unix, Unix-derived, or Unix-like. If anything, real Unix is becoming a mark of a proprietary OS.
The market is no longer patient enough to wait for vendors to extend or port operating systems to add new features and handle new hardware. For example, the comparatively small (but successful) commercial Linux player SuSE Linux AG managed in a few months to do what Microsoft Corp. and Sun Microsystems Inc. could not: Get an enterprise operating system running on the AMD64 platform. Working hard on Opteron gave SuSE the chance to be first to market, but from the beginning, SuSE turned all of its work over to the entire Linux community, no strings attached.
That's how Unix used to work. Those who now grouse about the dangers of relying on code written by students, academics, and casual coders forget that's how Unix got out of the lab and into business. Development tools and detailed documentation of Unix internals were standard issue. If a driver didn't exist for a new device, or a draft networking standard wasn't yet implemented in software, somebody who didn't necessarily write software for a living would create it. Then, more often than not, the programmer would give it away. Every commercial OS grew its own collection of contributed software and pulled the best pieces into the core software. Except in specialized markets, no operating system could flourish without that external involvement.
If your minimum acceptable standard for Unix is an operating system derived from AT&T's original work, you're missing out. The inclusive attitude and general openness that made Unix happen in the first place don't exist in HP-UX, AIX or Solaris. That magic is now in the hands of the developers and vendors who are shaping truly open OSes like BSD, Linux, and Darwin. A point release of any of these operating systems incorporates more and more worthwhile changes than their commercial counterparts. Testing and code review are thorough to the point of brutality -- a development manager at IBM or Sun would get fired for cussing out coders the way Linux and BSD committers (the anointed gatekeepers of code for the next release) do.
Unix vendors should have fashioned their efforts on the practices of Linux, BSD, and GNU instead of veering away from them. I get the irony that the free software movement came into being largely because of onerous Unix licensing terms. GNU is an acronym for "GNU's Not Unix." Some involved with free software may not want their operating systems referred to by a term they consider tarnished. I think of Unix as it was, not as it is today. To me, including Linux, BSD, and Darwin in the Unix category seems wholly appropriate given Unix's origins.