Well Declan, Priscilla Herdman has that as well unless she learnt it from Niamh (or you), but her CD is dated 2 years before Niamh's.

But as you say others can sing what they wish no problem.

Generally when words are printed in CD booklets they tend to be the actual published and therefore "copyright" words IME though the singer may sing slightly different ones, even if they wrote it.

I guess that depends on how strongly the publisher eels, some wont even give permission to publish the words although they generally cant stop you recording.