Could Microsoft block dual booting of another operating system such as Linux in its ARM version of Windows 8? That's the conclusion from Computerworld.uk.com which discovered a provision in Microsoft's Windows Hardware Certification Requirements, which were first posted in December.
The story gives its attention to page 116 of Microsoft's document which states:
MANDATORY: Enable/Disable Secure Boot. On non-ARM systems, it is required to implement the ability to disable Secure Boot via firmware setup. A physically present user must be allowed to disable Secure Boot via firmware setup without possession of Pkpriv. Programmatic disabling of Secure Boot either during Boot Services or after exiting EFI Boot Services MUST NOT be possible. Disabling Secure MUST NOT be possible on ARM systems.
This would seem to indicated that Microsoft is not allowing Secure Boot to be disabled on ARM-based Windows 8 hardware. There's no indication as to why Microsoft would make this kind of exception.
Back in September an employee at Red Hat expressed some concerns that Microsoft would not allow Linux to be dual booted on a Windows 8 PC. Microsoft later said that such a move would in fact be possible but that it would be up to the hardware manufacturer to allow users to disable secure boot on their devices.