
Microsoft will publish in the kernel of Linux its code under GPLv2

This initiative is aimed at promoting and improved support under the Linux platform of the Hyper-V virtualization server, a relatively new successful Microsoft product.
Microsoft previously entered into virtualization partnerships with Linux vendors Novell and Red Hat.
Such things, guys :)
via techflash.com
PS:
official Microsoft press release www.microsoft.com/presspass/features/2009/Jul09/07-20LinuxQA.mspx
20,000 lines of device driver code
video will be published with Sam Ramji, Senior Director of Platform Strategy Microsoft, on this topic channel9.msdn.com/posts/NicFill/Microsoft-Contributes-Code-to-the-Linux-Kernel