this is the internet right? http://arstechnica.com/business/2012/04/linux-kernel-in-2011...

>A new addition to the list of top contributors this year was Microsoft. The Redmond giant was the 17th most prolific corporate contributor to the Linux kernel in 2011. The company first began contributing code to Linux in 2009 when it submitted patches to improve the performance of running virtualized Linux guest instances on Windows servers.

That's not nearly the same as "Microsoft contributed most lines of code to the Linux kernal"

"17th most prolific corporate contributor" != most lines.

It provided a lot of lines of code, and it was the main contributor one year IIRC. But most of that was Hyper-V related code, to make Linux work better as a virtual machine guest over Windows.