Jon,
I realise that I am generalising, but one of the main differences between the two types of song for me is that while the traditional ones have been composed in a universal manner, thus enabling them to be taken up, adapted and used to represent different people and communities, the singer/songwriter type are, more often than not, introspective and private.
Some of the songwriters of the early revival (MacColl, Tawney, Rosselson, Guthrie etc, and even Dylan for a short time) set out to create universal songs, and they will, I believe, be with us for a long time to come. Quite honestly, I find the subject matter and form of most of the modern ones indistinguishable from that of the pop repertoire. I really can't see them being taken up and adapted, nor can I see them surviving the life or interest of the composers. Apart from anything else, the custom of copyrighting them will go a long way towards making sure of that anyway.
Can I make it clear that I am NOT making a value judgment on all this. Some of our most beautiful and important song and poetic literature is introspective. The traditional compositions reflected aspects of the communities, or trades, or ways of life - thence lies their importance and their difference.
Dave;
"when the composer is not known, we cannot say if they made any money out of the song or not. Can we?"
I would have thought that if the songs were being sold, the composers name would have survived, as did those of Waugh, Bamford, Hogg, and the host of local minor songwriters and kail yaird poets. Even the compositions that made it to the broadside presses seldom came with an named author.
The fact of the existence of a huge body of anonymous material dating back centuries and surviving (in some cases) into the mid 20th c. surely reinforces this.
Jim Carroll