Loose Rivets,
Have you actually read the license concerned (which is the thing the user is legally bound to, rather than some extract from a summary document produced by another department within Microsoft).
Section 2.....
“System Builder” means an original equipment manufacturer, an assembler, a refurbisher, or a software pre-installer that sells the Customer System(s) to a third party.
Therefore I would put forward that it is quite clear, even to non-lawyers that a "home-build" does not qualify for an OEM license.
(I am not a lawyer, nor do I work for M$ .... so am willing to be proven wrong ... but some blog post by a journo doesn't quite cut it !
)