Oh, yeah - also SunOS, Solaris, HPUX, Sequent Dynix and Dynix/ptx amongst others I've likely forgotten existed.
We used a ton of SCO Xenix / Unix / Unixware at a previous employer. We used it to build fax and interactive voice response servers and push rack/port densities that we could only dream of with the older (DOS-based) units. IRC, we could push only 16 ports per cabinet with the DOS units, but 128 with the Unixware boxes. Pretty big win considering we had customers that had 10+ *racks* of the DOS units in production (this was during the mid-90s, today those port densities would be laughable).
We used a ton of SCO Xenix / Unix / Unixware at a previous employer. We used it to build fax and interactive voice response servers and push rack/port densities that we could only dream of with the older (DOS-based) units. IRC, we could push only 16 ports per cabinet with the DOS units, but 128 with the Unixware boxes. Pretty big win considering we had customers that had 10+ *racks* of the DOS units in production (this was during the mid-90s, today those port densities would be laughable).