Comment they're doing the same thing as Apple (Score 1) 69
Why does anyone find it surprising?
If you register for a developer program you'll be able to (for a fee) compile and develop apps and sign them for your device. If you want others to be able to run them you'll submit them to MS' store and they'll approve them or not.
And yes, just like for iOS you'll be able to do development and testing on the device.
It's been done before by Apple and by MS (for Windows and Windows Phone). I'm not sure what is the shock that it's going to happen again.
They're going to be Windows apps and they'll likely run in the Xbox dashboard, not "beside it" like the disc-base games do. Snap-ins, etc.