Man, every post from Raymond Chen regarding Windows internals is like a little Xmas. I wonder whether he has to ask someone for permission before publishing this knowledge, though.
Being tenured and one of the top engineers in your company with a very proven track record gives you quite a bit more freedom.
Which sort of makes sense. I'm not sure technical trade secrets have ever played much of a role in Microsoft's success.
With or without source code, programmers have been digging at the internals of Microsoft OSes for fun and profit since the DOS days, and Microsoft has always seemed to recognize that developers and customers relying on the undocumented nuances of their products benefits them far more than understanding them benefits their competitors.