IIRC there is no such rule in Windows Store (http://msdn.microsoft.com/en-us/library/windows/apps/hh694083.aspx http://msdn.microsoft.com/en-us/library/windows/

IIRC there is no such rule in Windows Store (http://msdn.microsoft.com/en-us/library/windows/apps/hh694083.aspx http://msdn.microsoft.com/en-us/library/windows/apps/hh69408... ), just there is no browser engine which would satisfy technical requirements of sandbox (no executing generated machine code means no JIT, all GUI must be implemented trough WinRT APIs or DirectX and probably many others).