Do they share the code for the windows update mechanisms and the code for cortana and other spyware that is installed by default in windows?

I have no idea. I haven't used Windows in a years. Give it a shot. The most they can do is tell you no.

Put some effort in and reverse engineer it, if you really want to know how it works.

Complaining about the lack of source code is just sheer laziness.

How do you "ask them"? Do they have an email address for this? Or do you have to find the right guy on the team somehow?

Windows Shared Source initiative has existed for what, over 10 years now?

https://www.microsoft.com/en-us/sharedsource/

I think this "leak" is greatly exhagerated.

I haven't worked directly with Microsoft for well over 15 years, but this sounds similar to what I remember. Back then I worked for a partner who was doing direct integration work against low-level SQL Server and Windows libraries. Often when we encountered obscure bugs, they'd just give us the SQL Server or Windows source code and basically say, "Fix it, and we will release a hot fix." All of the comments would be replaced with white space which made things more difficult.

None of those categories seem to include ordinary developers though?

If your company, or you, have a relationship with Microsoft, try the Enterprise. They are pretty lenient, though not always rapid in their responses.

But the point is you need to already have a relationship, right? It seems you can't just say "I'm curious" (or even better, "I want to track down X bug") and expect to get source access, contrary to what was claimed earlier... Enterprise specifically says you need to "Maintain 10,000 Windows seats" which is not something a lone developer would do...

My only tie was having an MSDN subscription.

And you got it through the Enterprise license? Through your company or personally? Nothing related to 10,000 Windows seats? That's pretty weird if so since they say you must meet that requirement...

I didn't misrepresent myself, was logged in, and had no issues. They may have changed it, but that is what I selected. You'll probably have to sign an NDA. Give it a shot.

Even community MVPs get access to this stuff.