George, as far as I know you'd need the copyright holder's permission to make any adaptations and thereby become a co-owner of the copyright, so that's a bit of a circular argument. A few minor changes (Nic Jones and my words, Martin Simpson and my chords and timing) don't count as adaptations. To get your hands on a piece of the copyright you have to make substantial alterations (with permission), otherwise it's plagiarism, as far as I understand it.

Anne