If the US Government can't keep its most secret codes and data secret, how well do you think Micro$oft has been doing over the years with something that thousands of people all over the world have to deal with on a regular basis. Yeah, they could sue the daylights out of you but they don't have the investigative and prosecutorial power of Uncle nor can they impose the death penalty, at least not legally.
The leakage is only a portion and so far hasn't resulted in anything malicious, mostly because as noted above, anybody really capable of serious world-wide maliciousness (both technically and ethically) would already have compromised the code and used it if they could. An NDA, like a TRO, is just a piece of paper. It says "DON'T", but it can not and does not prevent the occasional "DO", especially with the type of folks that "WILL". Besides, if someone wanted to compromise Windows, there's so many holes in it, most of which haven't even been discovered, there's no need to have the code itself. I mean, how many security issues are there with Windows in the average month?
So, No Big Deal. A Tempest in a Teapot.
If anything, this points up the need for a serious competitor to Windows, one that works and is not full of holes and doesn't rely on secrets to be secure. Oh yeah, it has to be well accepted by the application community too.