It's interesting to note that Zimmerman's A Text (first) is titled 'Green on my Cape'. He dates it 'c.1800', which means that he didn't know the actual date. This song does not bear (very) much resemblance to 'Wearing of the Green' - but the 6th verse is,
In Brest [France!] I met Emmet who took me by the hand,
And asked me for Ireland and how did it now stand,
Such a poor distressed nation you hever have seen,
They hang men and women for wearing of the green.
Could it be assumed that, since Emmet was in France (Paris) from about November 1800 to October 1802, the song could not have been written prior to late 1800? I have a very good modern study of Emmet (Prof Marianne Elliott's) but she doesn't say which port Emmet sailed out of France from, only that he landed in England and then travelled on to Ireland. If it were Brest, could the song pre-date November 1802? (He entered France from Germany).
Zimmerman also refers to 'Another Wearing of the Green by Henry Grattan Curran in Barry's Songs of Ireland, p.144'. Can anyone access that?
So there are at least three versions. A biograper of Boucicault, Richard Fawkes (1979) states that Boucicault learned the original from the singing of his mother Anna Maria Darley (born 1794 or 95) and rewrote the version that we all now know for his play 'Arrah-na-Pogue (Arrah of the Kiss), or, The Wicklow Wedding'. This was first produced in Dublin on 7 November 1864.
However, when the play was produced in the US about 3 years later, both the play and the song were jointly credited to Boucicault and and an American journalist called Edward Howard House. Mr House is definitely thought to have had a hand in the rewrites but nobody can say with certainty who actually wrote what.
So as far as I can see, we have, at least, the original song (1800 or later), Curran's effort, and the one by Boucicault (and to a lesser extent Edward Howard House). I suspect that if Boucicault had never lived, none of us today would know 'The Wearing of the Green'.