Apparently, Microsoft is planning to block any alternative operating systems from Windows 8 on ARM-based devices. As Glyn Mood noticed and published in an extensive ComputerWorld report hidden underneath the technical provisions of Windows Hardware Certification Requirements there is a decisive clue to that fact. The demonstration relies on the fact that devices running on Windows 8 come with secure boot enabled.
There are however two alternatives. One would mean that Windows should sign in with a Microsoft key and this key to be partially included with all the systems. The other solution would mean that each OEM would have their own key and sign the pre-installed versions of Windows. The second option would imply several limitations, as Glyn Moody article points out. This solution “would make it impossible to run boxed copies of Windows on Windows logo hardware, and also impossible to install new versions of Windows unless your OEM provided a new signed copy.” Therefore, a system that has only OEM and Microsoft keys would not allow a generic copy of Linux.
Besides, somewhere on the page 116 of Microsoft’s Windows Hardware Certification Requirements for Windows 8 there is an explicit interdiction: “On an ARM system, it is forbidden to enable Custom Mode. Only Standard Mode may be enable.” [sic] Nor will users have the choice to simply disable secure boot, as they will on non-ARM systems: “Disabling Secure [Boot] MUST NOT be possible on ARM systems.”