Vaughan Williams has made folk songs something else entirely - he ised the tunes, not the words
Martin Carthy should know better than to copyright folk songs
The only time MacColl ever fell out with Like Kelly was when the Dubliners copyrighted folk songs he learned when he was living in England   
Says a lot about Ewan that he would point that out to a friend, just as it says a lot about Kelly who took his advice
All folksongs are arrangements by their very process of continuation
Jim