Just a few thoughts on this post:
"2) Distribute under the GPL."
"Microsoft need an App store to compete with the convenience of Apple and Linux distros."
These two competitors to Microsoft who don't have desktop app stores?
"When they have an App store, they remove distributors' motivation to pre-install Windows. When that happens, Microsoft will have to compete for real."
Have you seen mobile carriers desperation to get the iPhone due to its huge app store? Thats assisted by a big developer base supporting the iPhone SDK, on the Desktop Microsoft are developer kings, whatever people say they just are with the vast majority of software compatible with the PC, therefore an app store for Windows would provide a massive revenue stream for developers and Microsoft (if they follow the 30% cut Apple take) as well as provide additional functionality/value addition to hardware vendors who'll then seek to follow the platform with the largest app store. Which at the moment is Microsoft....