Irish programmer Steve Troughton-Smith has revealed that he was able to run an early version of Apple's OS X server operating system on a Surface tablet From The Verge:

Microsoft locked down its Windows RT operating system to new Windows 8-style applications, rather than allow developers to compile ARM-based apps. Irish programmer Steve Troughton-Smith has tried the technique on his Surface tablet today, revealing that he was able to run an early version of Apple's OS X server operating system on a Surface tablet. With XDA Developers members eager to test the jailbreak, it's possible that Windows RT might develop a healthy homebrew community for desktop apps providing Microsoft doesn't attempt to patch the flaw in future.

Early Mac OS seen running on Surface thanks to Windows RT jailbreak