If that's what happened well it sucks to be him but technically under the Geneva Convention and current laws of war, the US is allowed to hold him until the war ends at which point it must try him before a court (which can be a military tribunal) or trade him for it's own soldiers who are being held as POWs (which doesn't really happen because Al-Qaeda murders most prisoners).
Also small quibble with your story, he's been held for less than 10 years not more than 20. He gets normal food and can talk with fellow inmates and his guards, he is not urinated upon nor does he claim he was tortured, aside from being force fed. He does have access to all sorts of entertainment, so there isn't quite 1:1 parity here.
And for the record: a hunger strike (to death), like suicide is not I repeat not EVER an acceptable form of protest. Suicide is a cop-out, and a principle =/= a life.
a life >>>>>>> a principle.
To take your life in a form of protest is to admit you are wrong.
Also someone just posted a link to his Dossier and this guy is far from innocent: He admitted to fighting for Al-Qaida, he is mentioned in Al-Qaida documentation, regarding UBL.
So there you have it: he wasn't "walking in the forest to check out wildlife".