I had heard of Xenix over the years, but I hadn't realized they essentially upstreamed to the x86 port of SysV and continued to receive royalties for it, which it says very briefly at the end of this article.
I think that it was v7, I remember that it was SCO who did the SystemV 286 port (I know this because SCO brought the company in that I worked for when they got stuck working on the MMU, .... and then screwed us over .... long before the whole Linux legal kerfuffle).
I'm also skeptical of the comment at the end about MS getting paid for all x86 Unixes, I'm sure that was true for anything labelled "Xenix" probably not true for 286 and later SysV ports which were done outside of MS
I think SCO (SCOC not SCOX) ported so much of their own and MS stuff from Xenix 2.3.2 to 2.3.4 over to SCO UNIX SysV 3.2v2.0 to keep MS Word working I can well imagine (and I think I recall) that MS got royalty kick for every SysV Release 3.2 x86 install.
I remember finding Microsoft copyright statements in some programs on a Solaris 7 box in 2000 (my memory says /bin/true but some googling reveals it was probably /usr/bin/clear). Some of these programs were implemented as shell scripts and had copyrights from SysV, some of which had come from Xenix.
