Sorry if I'm splitting postings but I've spent ages typing out long threads recently and in the past only for them to disappear into the ether.

IFMC history. In 54 reps from many countries (about 60 I think) got together to come up with a working definition, at the instigation of Annie Gilchrist of the EFDSS (and president of IFMC) and a few others. There was a lot of disagreement even then as you would expect with so many different traditions. Quite a few of those present wanted to include all sorts of stuff others wouldn't allow in. In the end they had to accept democratic vote which they agreed to and the definition was actually drawn up by AGG and approved by the majority. Even this had to be tweaked a few months later as one of the descriptors in the original had been that folk music must be anonymous, yes, I agree, ludicrous and unworkable. It was immediately dropped after several noted folklorists pointed this out. (I can expand if necessary). Since the 'definition' was adopted there have been all sorts of holes poked in it. I think it still stands because there is no longer enough interest in folklore matters internationally to be bothered to change or qualify it.
All of this is from memory (I was only 7 in '54 but I had read the wonderful Opies' book on childlore) so it might not be totally accurate.
Having said all that, in my own researches it still is workable as a crude set of guidelines and I do use it, as do other researchers in the field. I do not however know anybody, scholar or academic, who tries to apply it rigidly.