Again, so too is z/OS a complete UNIX system (from the user perspective). OSF/1 is decidedly not the the BSD side of the Unix wars, it is its own alternative s

Again, so too is z/OS a complete UNIX system (from the user perspective). OSF/1 is decidedly not the the BSD side of the Unix wars, it is its own alternative strand against its contemporaries BSD and System V. More specifically, it took its initial UNIX personality from IBM AIX and was rapidly developed and redefined to accommodate the standards du jour which included BSD and System V APIs.