The question in my mind isn't "is Android open/free" -- it is. Anyone can download it, modify it, redistribute it, do what they want. And people have shown that you can even load other versions of Android onto the devices (hacked versions of Android, pre-releases of Android installed manually, etc.). Things layered on top of Android (the HTC Hero's advanced UI) aren't open/free, but that's not any different than Gnu/Linux. From an openness and freedom point of view, Android isn't any different than Gnu/Linux.
Android, on the other hand, is built around a GPLed core.