I'm not totally sure.

folksinging is a funny thing.
I knew Black is the Colour from Hamish Imlach and Joan Baez, and even Derek Brimstone. To be honest I never reckoned much to it, til I heard Christy Moore's version.

he did it in a way that suddenly opened up the song thousands of singers througout the English speaking world.

Does he deserve recognition and rights of possession to his arrangement, I think maybe yes.

Does he deserve ownership of the song for all posterity. No.

Its only what Vaughan Williams and benjamin Britten have got for their arrangements. Why shou;ld it no extend to lowly folksingers in folk clubs.

I'm not an expert, why would I know better than you. just thoughts...