Microsoft is seeking to take a more responsible role in the realm of PC security, and as such is launching a program to assist third party Windows software developers in locating and fixing security bugs. The Microsoft Vulnerability Research team isn't making a whole lot of new waves, as Microsoft already does to an extent help external software vendors in fixing security flaws, but brings the entire scope of that work into one name.
The basic idea is to report vulnerabilities as they are discovered and then, if needed, help develop a fix for them. This is almost a mirror image of instances in the past where Microsoft has delayed a fix for a critical security flaw and a third party has created a patch for it in the interim.
Though Microsoft is willing to assist other developers, they made it clear that the Windows Update service is, and always will be, exclusive to Microsoft products (excluding driver updates) and they will not be working on any system in which all installed software can be periodically checked for updates. This is an advantage that operating systems like Mac OS X have, in which larger ranges of software can be updated all at once.