because you don't own the software. You buy a license to use it the software. You dont' "own" it. Read the EULA.
Perhaps you can point to the part of the EULA, Ill help
1. GRANT OF LICENSE. Microsoft grants you the following rights provided that you comply with all terms and conditions of this EULA: 1.1 Installation and use. You may: (a) install and use a copy of the Software on one personal computer or other device; and (b) install an additional copy of the Software on a second, portable device for the exclusive use of the primary user of the first copy of the Software.
Hmm I think a Linux box counts as a personal computer no? Now I am sure MS can sick a team of lawyers on anyone but do you really feel this is not an anticompetitive by MS?
Hack the software. Problem solved.
I dont care what the EULA says. I paid money for software and the copy is mine. If they want to revoke my use I'll get a hacked copy, I dont care. And this from a computer programmer.