It strikes me that language being what it is, the term 'folk song' irrespective of it's 1954 definition, has well and truly evolved in contemporary understanding into something far broader and more inclusive.

And now that it is so completely owned by a more popular understanding, there seems IMO little point in attempting to reclaim it, or preserve whatever integrity it may (?) have once possessed.

If academics want a term that isn't open for evolved reabsorption into the language, probably better to utilise a far less ambienced word than 'folk' for starters, preferably one with lots of unfriendly syllables, and a very stingy amount of entries in the dictionary... ;-)