Think of it like this: Google has Android for mobile devices, ChromeOS for Internet appliances, and runs on full-fledged desktop OSes through the Internet (and their own Chrome browser).
Apple has it’s own full-fledged desktop OS, and an OS for mobile devices. As an appliance device, the RAT will have it’s own OS.1
Keep in mind that this is completely the opposite to the Windows approach to tailoring the OS to the device, i.e. “one size fits all”.
- The unmentioned fourth OS of course is Mac OS X Server. ↩