Since I've already been PM'ed about this a few times, I thought I'd say that yes, the WRK kernel posted here is valid and not technically leaked, but it is only available to be used legally by persons enrolled in, employed in teaching at, or involved in research at higher education facilities:
Eligibility Requirements:
Use of the Windows Research Kernel requires academic affiliation with an accredited institution of higher education and direct involvement in teaching and/or research, such as being academic faculty members, system or lab administrators or instructors, students enrolled in relevant undergraduate or graduate programs, or academic researchers working on faculty sponsored projects.
http://www.microsoft.com/resources/shareds...archkernel.mspx
However, since this is only supposed to be available via MSDNAA, I'd say this is pushing legal limits in some countries.