I was hoping to read that if you promised to publish only FOSS on the app store you wouldn't have to pay for the yearly developer's account fee. Too bad, that's not there. To develop for windows phone 8 / windows 8 and be able to test on real phones and publish on the app store, you need:
- a yearly 99$ developer's account fee
- a windows 8 pro 64 bits installation to run visual studio 2012
- to test on the emulator, a computer with a CPU supporting SLAT; therefore either a pretty new PC or a virtualization software that supports it, like the latest Parallels Desktop, which is not free either
Once you pay for all that making your software not free anymore is almost natural.