---ACTIVE DUTY includes RESERVES as well (since duty is still *active*). I am not sure about retired. The Military Discount is offered to EVERYONE sailing in the same stateroom.
Reserves qualify if they were activated within the calendar year prior to sailing. Retired are treated just the same as active duty.
A military member can reserve up to three staterooms. The military member has to be sailing with the rest of the party.
From DCL Website...
Special Military rates are available to all retired and active U.S. Military personnel, including U.S. Air Force, U.S. Army, U.S. Marines, U.S Navy, U.S. Coast Guard, U.S. National Guard, U.S. Army Reserve and U.S. Department of Defense personnel. Active and retired members of the U.S. military must provide valid identification at time of check-in. This offer is limited to a maximum of 3 staterooms per military member, per sailing. A U.S. Military service member is required to sail to take advantage of this offer. Activated members of the U.S. National Guard or the U.S. Army Reserve must also show active duty orders (active duty papers must be dated as of January 1st of the previous year to qualify).