There are multiple licenses - OEM, Retail, Upgrade - you can absolutely
use Retail... but not OEM.
Your link to Microsoft seems to say essentially the same thing as the
blog entry (partially quoted below). Though it does look like the
trimmed a few words, I still read it as essentially the same. Meaning it
is not legal to put an OEM copy of Windows on a Mac - Apple has to do it
for you (and I don't think they are).
My source:
http://blogs.msdn.com/mssmallbiz/archive/2005/09/07/461950.aspx
To quote the blog entry:
"4.1 We grant you a nonexclusive right to distribute an individual
software license only with a fully assembled computer system. A "fully
assembled computer system" means a computer system consisting of at
least a central processing unit, a motherboard, a hard drive, a power
supply, and a case."
You will notice the loophole that people have been exploiting (the
former language which stated that an OEM desktop Operating System
license could be sold with "non-peripheral hardware,") is no longer in
place. It is now very simple and straightforward: an OEM license must be
sold "only with a fully assembled computer system." Loophole closed.
Also, in section 6. Preinstallation requirement, you will notice it now
states:
"When you distribute an individual software license for a desktop
operating system or application software, you must preinstall it on the
fully assembled computer system’s hard drive using the OEM
Preinstallation Kit ("OPK") provided in this package or otherwise made
available by us. This preinstallation requirement does not apply to
server software."
So in addition to having to sell an OEM Desktop Operating System license
with a fully assembled computer system, it must also be preinstalled on
the fully assembled computer system that it is being sold with. Again,
loophole closed. These same restrictions would also apply to any OEM
Office license as well. OEM Office must be sold with a fully assembled
computer system and must also be preinstalled on the fully assembled
computer system that it is being sold with. OEM Server licenses must
also be sold with a fully assembled computer system; however, the
preinstallation requirement clause does not apply to OEM server licenses
as you can see in section 6 above.