The headline really doesn't hint at the nuances of this.
Microsoft released code to help Linux run in Microsoft's HyperV virtualization system. Linux would run, just slower, without these drivers.
Releasing these drivers is likely a crucial step in getting HyperV adopted outside of windows-only shops. Linux is a popular server OS. It is crucial that they appeal to a large demographic, as they are competing with other established virtualization vendors like VMWare.
MSFT have certainly matured a lot in recent years. Windows 7 is looking good and now they are contributing to open source projects. I think we can thank Apple for forcing them to adapt.
To start with, Windows 7 is great but XP was pretty solid for its time too so I'm not sure that Win 7 signals anything other than the fact they've had a new hit.
However, there are segments within Microsoft that are working hard to get some momentum for what might otherwise become a stagnant behemoth of a software company. These cases are seeing Microsoft compromise old values in an effort to create something new (for instance this as you've said and ASP.NET MVC as another example).
Obviously it's all for profit but it's a good sign that it is still profitable to innovate, even in a company whose established popularity and size would typically mean that it stands to gain most from focusing on the "whole product" (e.g. support etc.) if we take Moore's chasm viewpoint.
Whether we have Apple to thank for this I'm unsure though. I guess the marketing efforts of Apple to make it cool have put a lot of pressure on Windows in the last few years. Whether the way to beat this marketing attempt by Apple is innovation is a deeper question.
I don't know about really apple moving them to adapt in this case. It seems to me that this is a response to the popularity of linux in server environments. They want their virtualization software to support linux. This doesn't detract that both parties benefit from it though.
Microsoft released code to help Linux run in Microsoft's HyperV virtualization system. Linux would run, just slower, without these drivers.
Releasing these drivers is likely a crucial step in getting HyperV adopted outside of windows-only shops. Linux is a popular server OS. It is crucial that they appeal to a large demographic, as they are competing with other established virtualization vendors like VMWare.