My scenario:
the co-pilot takes over
The pilot is having a heart attack and receiving first aid, the co-pilot takes over. Before landing the pilot dies. The co-pilot is now the "pilot" because a single person flying a plane is the "pilot". A co-pilot flying by himself is no longer a co-pilot. A co-pilot is a fully trained pilot, co-pilot is just his status on that plane (dict: "The second or relief pilot of an aircraft", which he can't be if there is only one pilot ).
and lands the craft safely with no casualties other then the pilot who survives to live many more years
The pilot (former co-pilot) injures himself during the landing, becoming the casualty.
so in this context we can assume casualty to mean any form of injury or harm.
A casualty has to get harm/death from the incident.
(dictionary: "One that is harmed or eliminated as a result of an action or a circumstance"; "One injured or killed in an accident")
Someone dying of natural causes unrelated to the incident isn't a casualty. In this case it doesn't say the heart attack is caused by stress/injury, so its an assumption either way, I'm assuming its not related.
the co-pilot is not considered a full pilot for the purpose of the question.
But a co-pilot is a fully trained pilot by definition. He's only the co-pilot while someone else is in charge of the aircraft.
-----------
There are different scenarios: The original pilot gets the medal for using great skill to bring the aircraft down to the airport, the co-pilot gets nothing. But that's counter-intuitive (besides being the most obvious) to the fact that neither pilot single-handedly saved the plane, it required the effort of both pilots, which implies both are deserving of merit, IMHO.
In my scenario, the biggest problem is assuming the pilot isn't the casualty even though he's dead, since it would be difficult to show that the heart attack was completely unrelated to the stress of the situation.