In fact, WOA only supports running code that has been distributed through Windows Update along with the full spectrum of Windows Store applications.
WOA PCs will be serviced only through Windows or Microsoft Update, and consumer apps will only come from the Windows Store, so you never have to worry if a program will run because you are not downloading or installing from a DVD outside of the store experience. A WOA PC will feel like a consumer electronics device in terms of how it is used and managed.
Ergo, they probably won't be working hard to lock the platform from other applications (what little applications that will exist, that is)
Where something sits on several axes of flexibility is certainly interesting and can be cause for concern, but let's lose the nonsense disproved by real software.
There are a few, and we could probably enumerate them all right here. The reason they stand out is that almost no one does that, and that it's not an effective development environment for most people.
Personally, I'd sooner shift careers to road mending than try to program on an iPad.
And, personally, I'd love to be able to run Xcode on an iPad. With a Bluetooth keyboard it would be practically identical to the laptop I use now, but better for my back and wrists.