How open is the source code of android phones? I cannot think of a way that manufacturers can close their drivers, because they have to conform to the GPLv2 as the License of the Linux kernel states. Or do they use write a large part in user space code, where they can choose their own licence?
The information I'm trying to get here is: How difficult is it to get a "cheap" smartphone (htc wildfire-s) and run Linux on top of it full featured. What I mean is every hardware feature is easily accesible without having to implement your own drivers and reverse engineer the device (assuming that the device is rooted).
I think I found my answer at last. A lot of firmware of a lot of android phones is delivered binary only. Which makes it less open. If I want to run GNU/Linux on top of a stock phone I run in a lot of those issues. See Richard Stallmans article on how free android is: Is Android really free software?
There is also a project Replicant which tries to create a free (FSF definition of free) android based stack.