That said, I can't imagine Linux actually having gone very far if it wasn't a UNIX clone. I think it would have been a real long uphill battle and it would have gotten handily beat by whatever open source UNIX clone came along next, for the pure reason that it's much easier to deal with POSIX compliance (and all the software it brings that actually makes it worthwhile to run the OS) when trying to copy a system that already did it and worked out the kinks.
I mean, if someone came out with a free (maybe open source) version of Windows at that time which was legal, we could easily be living in a world where that's the dominant free OS.
I guess what I'm saying that that being vastly better on one metric (in this case, free) doesn't necessarily mean you'll take over a market (because a free operating system that can't run any software isn't very useful), and just being a clone won't either, but being a clone that's generally as good one most metrics and vastly better on a few others (e.g. a UNIX which is also free and open source, instead of just some other UNIX) may.
One thing is for certain: you will not replace the current players by cloning them.