In their defense, lots of people have done so
It's not like Christy Moore is the one who wrote the song. Actually, I think its origins are pretty much unknown.
Plenty of people have taken a stab at it. So did Cara Dillon. And then 2Devine did their bit. Finally, Above & Beyond gave us the remix that we love so much.
I wouldn't really call it stealing. The lyrics and the arrangement of the song are really good, so I'm sure plenty of people would like to do their own bit and play it the way they deem it best (just like Christy Moore did in fact). The fact that it's a folk song with unknown origins just makes it easier for people to do so.
It was only a matter of time before we saw a trance version of it.
EDIT: Just saw your post above