Microsoft releases source code for Linux Vm ICs (Integrated Components) – formerly called VM Additions
Get the offical story here:
External Article on the Subject
"Microsoft stuns Linux world, submits source code for kernel "
First and foremost, the title is very misleading. We did not release any source code for "our" kernel. We released source code for virtualization support on Hyper-V to be included into the Linux Kernel’s source code.
This is an open source requirement as Linux operates off a more macro kernel and requires kernel re-compilation for driver support. This is, in essence, driver code, not Windows kernel code.
The next question you may have is: Why? Well, to quote the following article "Microsoft is making a compelling case that it could be the virtualization vendor of choice for consolidation of Windows and Linux applications."