Just today, Microsoft has contributed 20,000 lines of code to Linux, licensed under the GPLv2. This is the first time Microsoft has chosen to use the GPL to license it’s own code.  The software they’ve released today helps to make Linux work better when running in a virtual machine on top of Microsoft’s Hyper-V hypervisor.

Microsoft’s announcement was a big surprise coming from the same company who argued that the “[GPL] debases the currency of the ideas and labor that transform great ideas into great products” and have compared it to a virus.

While this is the first time Microsoft has released code under the GPL, it isn’t the first contribution Microsoft has made to Free Software.  For example, in January of this year, Microsoft made it’s first contribution to the Apache project.  Microsoft’s Bing search engine includes some open source code.  Microsoft also has it’s own Free Software license called the Microsoft Public License (Ms-PL) which is recognized as such by the Free Software Foundation.

Microsoft has also been showing support for Mono with promises not to sue Mono users for patent violations.  I was also surprised to notice that Microsoft’s video website, which requires the Silverlight plugin, redirects Linux users to Mono’s Moonlight plugin page.

So, what’s next?  Perhaps Windows 8 will run on the Linux kernel.