Wolfgang: now we're completely together on this, except for a little extra twist after the second shot. My complete answer to the version as set in New Scientist was.

It would seem clear that each duellist needs to 'take out' their most dangerous opponent at any opportunity. By this reasoning, George will shoot first at Ernest and, if successful will then be shot at by Fred. If George is unsuccessful Fred will shoot at Ernest, and if successful will be shot at by George. On this reasoning, Ernest's chance of being killed in the first round is 60% (killed by George) and 30% (75% of the remaining 40% shot by Fred) Thus, it appears that Ernest has only a 10% chance of getting to shoot at anyone.
However, looking at the odds for the 6 possible two man duels we see the chance for tactical shooting by George.
Ernest v Fred (with Ernest shooting first) Fred dies 100% of the time
Ernest v Fred (with Fred shooting first) Ernest dies 75% of the time, otherwise Fred dies on the next shot
George v Ernest (With Ernest shooting first) George dies 100% of the time
George v Ernest (with George shooting first) Ernest dies 60% of the time, otherwise George dies on the next shot
Fred v George (with Fred shooting first) George dies 75 % of the time, otherwise Fred dies 15%(60% of the remaining 25%). with the next round, George dies 7.5% and Fred 1.5% etc. Cumulatively, George's chance of survival is 16.66%
Fred v George (with George shooting first) Fred dies 60% of the time, otherwise George dies 30%(75% * remaining40%). With the next round, Fred dies 6% and George 3%. Cumulatively George's chance of survival is 66.6%.
From the above it is clear that George can massively improve his chances by ensuring that in any two man duel he gets the first shot. He can ensure this improvement to his chances by firing into the ground whilst there are still 3 men standing, and shooting at the remaining duellist once they are down to two. The only possibilities then are that Fred's first shot kills Ernest (75%) and George has a 66.6% survival rate. or Fred fails to kill Ernest, Ernest kills Fred and George has a 60% survival chance. George's overall chance of survival is thus (75%*66.6%)=50% + (25%*60%)=15% =65%

Shooting to miss cannot improve the chances of either of the other duellists. (without collusion). Of course, if George can work this out, then so can Ernest & Fred! As George must wait to shoot again, the other two could discuss these dirty tactics, and realise their own chances of survival.
If they both take their chances to shoot each other, Fred will survive into round two 75% of the time, and of this 75% will survive completely (75% * 33.33%)= 25% of the time.
If Ernest survives Fred's shot (25% of the time,) he can immediately kill Fred and have a 40% chance of survival against George. making Ernest's overall survival chance (25% * 40%)= 10%.
Thus Ernest's chances can be improved from 10% to 25% by the removal of George, with chances of Fred increasing from 25 % to 75%. Thus Ernest & Fred decide that George should die for cheating, Fred shoots into the ground and Ernest shoots George.
This relies on the honour of Ernest, after Fred shoots the ground, Ernest could shoot Fred and improve his own chances to 40%
It takes only a small alteration in the percentage rates in the question to throw up a large number of preferred strategies. At some closer percentages we could find all the duellists firing into the ground in turn!
Despite all my comments, I think the answer required is that George survives 65% of the time.