"Folk music" is the process of transmitting songs and sharing within a community.

I'd call that the "folk process". Folk songs are songs that came out of that process (which is now effectively over, or surviving in the odd cultural pocket, like Japanese soldiers on Pacific islands).

You can make a very clear scientific case that will show that Pete Seeger, the Weavers, Odetta, Ed McCurdy, the New Lost City Ramblers and others do not belong in the genre "folk music" - but what is the gain in that?

They're not part of the folk process - nobody, or hardly anybody, is - but they do or did perform folk songs, as well as songs that aren't folk songs.

glueman: What makes current songs unlikely to be taken up as folk (by purely traditional definitions) is that they are generally recorded and offer a perma-text for comparison which militates against transformation and the desire for recognition by the writer/singer.

Zigackly. Most music that most people listen to isn't transmitted orally, which in turn means that there just isn't enough oral transmission going on for the folk process to happen. Which in turn means that folk song is (in Nick's terms) 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

Having said that, folk songs are still being tinkered with and embellished and added to, by folk enthusiasts. New songs that sound like the old ones are still being written and sung and learnt by ear, by folk enthusiasts. Folk in performance is a living museum, and being part of it's a huge pleasure as well as a privilege. It's still a museum, though.