A folksinger is a person to whom a song was transmitted via the oral tradition and who sings it as such. He may also archive them. An example would be the late Stan Hugill, last of the shantymen. Another might have been Bert Lloyd. I suppose a case could be made that the Bob Copper is a surviving folksinger and that I exaggerated.

A folksong singer is someone who has learned folksongs via research, and now sings them. An example is Martin Carthy (MBE for services to folk music!)