For more information you can contact me at : snj8@unh.edu
The rise of Unix in the early 80s had much to do with economics and hardware, and little to do with Open Systems or any of the ex-post-facto justifications or explanations that have circulated. Quite simply, beginning with Sun Microsystems' first workstations, Unix was the software that ran on the best low-cost available hardware, and the number of Unix installations grew rapidly. You could put a workstation on everyone's desk, and still have spend less than a mainframe would have cost.
The other factor in Unix growth was education. Ultimatley, this also related to economics. Schools were turning out loads of very competent computer users (and systems programmers) who already knew Unix. You could therefore "buy" a ready-made programming staff. You didn't have to train them on the intricacies of some unknown operating system. It takes a long time to become an expert; with Unix, you can buy them ready-made. Also, cost other operating systems have remained more-or-less the same from their invention until there obsolescance. Once again, Unix's popularity was due to economics: users want new features, vendors want to sell new features, defeloping new features in-house is expensive.
Unix growth was immense in the early years of its development as indicated by this chart:
While the growth is stable, it is still strong, although not as it had been in the early years, when Operating Systems where being acquired by many different business organizations and universities.
For more information you can contact me at : snj8@unh.edu