Microsoft released 20,000 lines of device driver code to the Linux community under the General Public Licence v2.
The code includes 3 Linux device drivers & has been submitted to the Linux kernel community for inclusion in the Linux tree.

The drivers will be available to both the Linux community and customers, and will enhance the performance of the Linux operating system when virtualized on Windows Server 2008 Hyper-V or Windows Server 2008 R2 Hyper-V, according to the Opensource site of Microsoft, Port 25.

In an article posted to Microsoft's PressPass site, Tom Hanrahan, director of Microsoft's Open Source Technology Center, notes that this is a significant milestone because it's the 1st time Microsoft has released code directly to the Linux community. "Additionally significant is that we are releasing the code under the GPLv2 license, which is the Linux community's preferred license," he said.

Read more about this at the official Press Release.