It was played in Edinburgh sessions long before the Civil War series came out. Those session players got it on paper from the Scots Music Group (SMG) of the Gorgie-Dalry Adult Learning Project (ALP).

So now we know! That's where Jay Ungar gained those lucrative early royalties from - the Scots Music Group of the Gorgie-Dalry Adult Learning Project!

Local folk music organizations the world over reproduce stuff from commercial publishers all the time.   I would expect that ALP/SMG paid the going rate to Mel Bay but I wasn't there to check. They often explicitly credit copyright holders.


But did they not recognise that it wasn't actually a Scots tune?

They've never confined themselves to Scots material. Look at Nigel Gatherer's site, he included lots of (better) Americana early on.