And you can't easily rewrite Qt software to use GTK. Still they both run on Linux.

You probably could if Android weren't intentionally constrained by Google to prevent it. That's what fsflover is trying to point out: Android is more of a television firmware than an OS and counting it like a PC OS makes very little sense because you can't use it like one.

EDIT: I think you still don't understand. It doesn't matter what hardware Android runs on it's written to be appliance firmware. Even if you put it on a laptop it just turns the laptop into what is essentially a television.

	▲	palata a day ago \| parent [-]
		So I was saying that Android runs the Linux kernel, period. But now that you say it, Android is very much a full OS. It's not a Linux Desktop, but it is a full OS. And televisions running Android are called "smart TVs", precisely because they run a full OS instead of a minimal firmware like they used to. Google is working on bringing Android to the Desktop, and Samsung already does it. As in: you plug your smartphone into a docking station and it is suddenly a Desktop computer.