Leveller -
I tend to think that the songs need to be taken up and re-made outside the 'folk family' before they can be considered folk songs.
It might be claimed (though never by himself) that some of MacColl's Traveller songs 'passed into the tradition'; we recorded numerous versions of Freeborn Man from Irish Travellers. Jeremy Sandford in his 'Songs of the Roadside' even suggested (totally without substantiation), that MacColl had 'adapted' them from traditional Travellers songs; - one Scots 'academic' once claimed at a conference (again, without evidence) that he 'stole' Freeborn Man from a Traveller.
Even among Travellers, the song tradition seems to have disappeared, (we can almost put a date on it - sometime between August 1973 and Easter 1975), when they got portable televisions and stopped singing round an open fire.
Are you even 'anon' - virtually all the songwriters I know put their names to their compositions, many even hang a price-tag on them by copyrighting them, thus limiting their free currency.
Jim Carroll