The fact that 2 songs tell the same story or are based on the same event would hold no water in legal terms. To be recognised as the same song they would have to have substantial text/syntax in common. I'm not sure High Barbaree and George Aloe do have that. I could easily check. Or some sort of line of evolution would have to be demonstrated as with a piece like 'The Wild Rover' which almost word for word can be traced back to the 17th century. Ballads that tell the same story but have little text in common are Child 7 'Earl Brand' and 'The Douglas Tragedy', or another example 'Bruton Town/Bramble Briar' and 'The Constant Farmer's Son'.

However this is all irrelevant as 'The Coast of Barbary (High Barbary) is easily demonstrated as over 2 centuries old.