[dogma1138]

I'm not sure how many of them actually audited it and how many of them had to get access to the source code to tick a box.

Government contracts for software often include having the rights for the source code in case the vendor goes out of business.

In other cases they might want to audit only certain parts of the OS, or just to integrate their own code at a level that out of the box Windows interoperability doesn't support.

If you say have a hardware encryption & security module which connects directly to the hard hard drive and includes a smart card reader for access you will probably need the ability to run custom code in the BIOS, boot loader and OS levels.

Then again if you have the resources of a US, major European power, Russian or Chinese state agency you might have the ability to also audit the full source code.

[MichaelGG]

I had personal access to the Windows "shared source" system, as a third-party. Issued a smart card for remote access. It's not that hard to get and I know other individuals who maintain that access.

It comes in really handy for figuring out specific bugs or implementation details. I'd imagine any large-enough customer would find similar value.