Mozilla general counsel Harvey Anderson last May, regarding the restrictions of Windows RT that prevent a native Firefox app:
Unfortunately, the upcoming release of Windows for the ARM
processor architecture and Microsoft’s browser practices regarding
Windows 8 Metro signal an unwelcome return to the digital dark
ages where users and developers didn’t have browser choices.
Why does this matter to users? Quite simply because Windows on ARM
— as currently designed — restricts user choice, reduces competition
and chills innovation. By allowing only IE to perform the advanced
functions of a modern Web browser, third-party browsers are
effectively excluded from the platform. This matters for users of
today’s tablets and tomorrow’s PCs. […]
The prospect that the next generation of Windows on ARM devices
would limit users to one browser is untenable and represents a
first step toward a new platform lock-in.