Most open source board / best Android board

Hi everybody,

I'm looking for a board to hack on Android 4. I've seen that there are several ARM boards with Android community support: Origen, PandaBoard, Snowball, etc.

I'm interested in knowing which one is the most "open source" one, that is to say, which one relies on the least number of proprietary drivers (es. PandaBoard needs PowerVR binary driver for accelerated graphics, while the Snowball board Mali 400 GPU has an experimental open source driver).

I'm also interested in which one has the best support for Android, in terms of features supported (best Android port).

Thank you for any suggestion you'll give me!

Regards, Diego