Towers
..... and that is when all hell lets rip. Every copy of Mac OSX used BSD as its kernal. Maybe not in the Microsoft league but Cupertino does have a billion plus dollar warchest. However, is this the ultimate aim or the place Microsoft will stop shortof attacking?
I am not too concerned about BSD-derived Unices. The "open-sourcing" of BSD (Berkeley Software Distribution) Unix was doen directly between the UCB CSRG and ATT Research, back in the days when ATT still actually "owned" it for real" from the ground up (Unix was originally developed at an ATT research centre in the seventies) and was done, very carefully, with successively released versions of the code to ensure that when they finally went "ATT-free", everything was watertight license-wise (this was around about release BSD 4.3-Tahoe or 4.3-Reno, IIRC.)
(Trying to dredge up the substance of a conversation I had over a beer with Kirk McKusick of the CSRG about this very subject many moons ago
)
Crucially, BSD
pre-dates Linux by some way