from an app provided through their store that they don't get a cut of will soon find the app no longer available via their store. And since most of the apps for the Surface and Win 8 will only be available via their store due to their vendor lock-in system, well, I don't think you'll do well once they get on your case.
And from what I can access from the MS site the only free Win 8 apps are the ones they make themselves. The website s I've hit through their system is NOT easy to dig through, either
Keep Up with TechRepublic