Jim

Again so that I understand your thinking -

Is 'folk' song a historical thing that is now over - like Baroque music that finished in the 18th century and can now be played or "written in the style of" but not in anyway added to?

Within the various definitions and discussions there at the same time seems to be the suggestion that folk song can be added to - how does that happen in a world where communications are different and things are written down and recorded (in writing-in recordings-on video)?

If I take a song that, to me, is very much in the folk tradition what would you consider it is? Northern Tide by Linda Kelly is a favourite song of mine. I learned it from hearing it sung by Linda (and others) and I sing it to others who add it to their repertoire. If you don't know the song there is a verse or two here (it was done in practice so is not that cleverly sung so apologies to your ears in advance as it doesn't do the song justice).
Now to me it sounds like a folk song. Content-wise it feels like a traditional folk song. But by all the definitions and stuff it would appear that it can't be one. Is the only way for it to become a folk song to be changed over time to become something else? And if it isn't folk music what is it?