In case anyone else is searching for whether or not one could reflash with open source firmware and run debian, here's what I found:
http://forum.xda-developers.com/fire-hd/general/how-to-upgra...
Short answer : It is non-trivial.
http://forum.xda-developers.com/fire-hd/general/how-to-upgra...
Short answer : It is non-trivial.