I'm not familiar with any definition that insists on a combination of tunes and lyrics and anyway, the 'Occupy' theme is just a bait that people have risen to. If you want to re-define traditional tunes in a way that accommodates their entry into normal, i.e. popular usage with all the variation that encompasses, then that can only be to the good of the music.

I return to the point that the revival definition has no organising body, no trusted 'boot room' of sages who can be trusted to know what a folk song is or be petitioned to allow common sense to include later variations. That leaves the situation we have today - traddies who admit nothing without a few hundred years of variation while ensuring such changes are impossible in a traditional context, others who are traditionally inclined but trust themselves to know what a folk song feels like without a dictionary to hand, and a wider constituency who see folk as a format that includes the potential for any self-penned song. I'd suggest there's room for all those points of view and an informed appraisal that each has its merits as the music of the people, without the bun fight that ensues every time the topic comes up.