Folk Song can be any song sung in the name of Folk in a designated Folk Context"

This is a circular argument.

"A DFC is not necessarily a Folk Club."

I still don't understand how a "designated Folk Context" (club or otherwise) as you have described it differs from open mike night at a coffee house. I frequent coffee houses, and often visit open mike's when I'm out for a walk, and I have never found one referred to as a "designated Folk Context" (which does have the ring of apparatchik lingo). Further, the singers, musicians, poets, cranks and maniacs who participate in these sessions do not generally (in my experience) identify themselves as 'folkies' or 'folk artists' or anything like that. Presumably, though, they would become such if someone "designated" my local coffee house as a "Folk Context"(?) . . .