Peace,

Of course the songs were composed by individuals (unless they were composed by Fairies, Angels or little creeping things that lived in the skirting-boards of Tudor Manor houses and crept out at night and whispered them into serving maids' ears - sorry, got carried away there!).

Just look at that last bit of the 1955 definition again:

"The term does not cover composed popular music that has been taken over ready-made by a community AND REMAINS UNCHANGED, for it is the RE-FASHIONING and RE-CREATION of the music by the community that gives it its folk-character ..."

Thus the question of whether the composer of the song is known or unknown becomes IRRELEVANT once the song has been changed by the community. ANY song can become a folk song if it has been through the right process (ie. the process described in the 1955 definition).
The notion that folk songs are only those songs that have been composed by 'Anon.' is just plain wrong. To repeat, it is the PROCESS that a song has been through that determines whether it is a folk song or not - NOT its origin.