When you buy a computer with Windows on it, you also pay for the OEM license. When you build one yourself you can run a pirated version of Windows at no extra cost.
Seeing as he works for the Pirate Party, I don't think it's a stretch to assume he got his copies of Windows and Visual studio off The Pirate Bay.
Or he have an MSDN subscription which covers both Windows+Visual studio, and dont want to pay extra for an OEM license to something he already has the right to use.
I'm pretty sure that if your computer is for "mixed use" (i.e. you use for stuff other than developing software) then you can't use the Windows licenses from MSDN - you need to buy a regular license.
"Many MSDN subscribers use a computer for mixed use—both design, development, testing, and demonstration of your programs (the use allowed under the MSDN subscription license) and some other use. Using the software in any other way, such as for doing email, playing games, or editing a document is another use and is not covered by the MSDN subscription license. When this happens, the underlying operating system must also be licensed normally by purchasing a regular copy of Windows such as the one that came with a new OEM PC."
Presumably he still qualifies for that since he is just using Windows for development. The license you quoted just refers to using their software for anything else.
Seeing as he works for the Pirate Party, I don't think it's a stretch to assume he got his copies of Windows and Visual studio off The Pirate Bay.