Open sourcing the Kernel

I highly doubt it . The NT OS Kernel (ntoskrnl.exe) is where Microsoft enforces some of their commercial restrictions, such as the maximum CPU count for a given license .  It is also where undiscovered or unpatched security issues can do the most damage.   Therefore the source code is only available to some highly trusted organizations, such as certain governments, CPU designers (such as DEC's Alpha team) and some university researchers under Microsoft's long existing "shared source" initiatives .   Another more practical issue is that some of the code in this large kernel may be licensed to Microsoft under licenses incompatible with opening up source access to a wider community.

Fortunately, many kernel integration developer tasks can be done via the "Device Driver Kit" (renamed the Windows Driver Kit years ago) and the various 3rd party documentation explaining the deeper details .  I recommend taking the specialist master classes ("seminars") available from OSR (Open System Resources) Inc, those really made me much better at some truly advanced kernel coding I did 20+ years ago.  Note that those are master classes meant for already experienced low level system programmers, not beginners. Another resource is to look at the incomplete open source clone of the Windows 5.01 kernel that someone tried to make back when that was the current Windows version .