@Purple

This might be true in most cases, the manufacturer has certain closed source elements they deliver on top of the OS.

Nothing about Linux and GPL stops proprietary layers, why should it, you don't have to give up your intellectual property just because you run something on top of an opensource stack.

But in the case of Windows, everthing is closed source including the OS.

With Android the manufacture has no choice but to release a compilable source for the entire OS.

This is why Android is wiping the floor with competitors, this is why Apple is losing ground, this is why Windows phone will never amount to more than a paltry percentage of wanna be's.

And ... hats off to google, they are a big thorn in the side of legacy OSes like Windows, it helps keep companies like Microsoft from using illegal acts to compete which is never acceptable in the pursuit of profit.

Maemo etc were pretty open hence cssu can exist but as you say perhaps not fully open.

However being able to Root your device you paid for so you can tinker is not a measure of how open it is, just a part of the requirement.

Rgds