This will make Windows less secure in the short term, but as good and bad actors find bugs and Microsoft patches them, they will end up with a hardened product. Their OS is now effectively open-source.
Yup. It's the Windows Shared Source Kit, which is already mostly public. Many of the big security firms and government agencies already have licences to the full source code anyway.
The only thing this really gains anyone is it possible some non-public debug symbols might have been left in some builds. Not earth shattering.
My favorite takeaway was, "With every day that passes, that stolen source code is more and more out-of-date."
I remember hearing Windows source code leaks in the past (I see articles from 2000 and 2004) and remember hearing about problems with "clean room" implementations of open source SMB implementations.
Yeah, the fundamentals and much of the source code will probably stick around for many, many years. But this has happened before and I don't see why this is any more of a big deal.