I've been searching, on and off for weeks, for the "right" tabs for this tune. The open-G version I mentioned above (August 4) is all over the internet, in three versions that differ only in the level of detail and the introductory paragraph. They all seem to be the work of one Barry Hutchinson, who says he doesn't guarantee they represent the original, just his best approximation.

However, I'm pretty sure that the renditions I've seen and heard and want to emulate (Jed's, and that of a regular at Gogarty's in Temple Bar, Dublin) are in open-D tuning.

I finally found this one:

http://www.paulbrady.com/tablature/lakespontchartrain.asp

which is a bit ambiguous -- it is said to be in open D, but the tuning is described in detail as open D-minor: D A D F# A D. I suppospe the only recourse is to try playing the tablature two ways, with the "G" string tuned down one half step and also one full step.

Well, I think I have enough to work with now to start trying to learn this. I have very little experience and absolutely no comfort level with open and alternate tunings, but I'm motivated to learn this version of this song; maybe this will be the start of learning a whole new bag of tricks.