Absent Unix or a class of operating systems coming out of a similar tradition, the operating systems that came out of the minicomputer era (VMS, AOS/VS, OS/400, etc.) would presumably have maintained their roles to some degree absent Unixes displacing them. And it's very hard to see Windows NT not largely winning out in such a world. As you suggest, it was a close thing as it was and a lot of people thought Scott McNealy was tilting at windmills for not buying into Windows inevitability.
Of course, that raises the question of what about open source in that world. I'm not sure it was in any sense inevitable that open source would have played out as it did. Although absent widespread open source adoption it is hard to see how the Internet would have grown as it did.
Of course, that raises the question of what about open source in that world. I'm not sure it was in any sense inevitable that open source would have played out as it did. Although absent widespread open source adoption it is hard to see how the Internet would have grown as it did.