Or, at minimum, getting away with involuntary manslaughter:

“I have come to realize what I did was wrong”
Thus spoke Spc. Brian E. Cammack, who was sentenced to three months in prison over the beating death of a prisoner in Afghanistan. Cammack plead guilty to charges of assault and two counts of making a false statement. In accepting a plea bargain, prosecutors decided not to pursue a charge of maltreatment (I guess manslaughter wasn’t on the list of possibilities).

A manslaughter charge certainly is a possibility in a military court.
This pat on the butt plea bargain could be the a result of at a couple different things: 1) The guy really is giving up good info that will lead to more severe penalties for others (don’t hold your breath) and 2) this administration and its military still don’t think anything wrong has occurred and believe that too severe sentences in these cases will dampen ongoing behavior in the inquisition centers.