Won't be long (Windows 8 probably) before you have to pay a developers license to distribute Windows Applications (of course, if you pay for Visual Studio, it will come with 1-year free).
What's the point of creating a phone with an app store when you are going to charge people to develop for that store (whether they charge for their app or not)? If people want to charge, then Microsoft gets their cut. If people want to give it away, Microsoft still gets its cut (30% of nothing is nothing). No, rather than open their platform and increase its popularity by having more apps included, Microsoft wants to make a quick buck off the few developers willing to write apps for their platform. Why do you think Apple touts their 300,000 apps (even if 200,000 of them are fart apps)? Because people know with more apps, its more likely that whatever they want their phone to do "There's an app for that" (TM).