My point was that they were playing their own original music, not copyrighted by others - as I think you were pretty much aware. The waiver was about not playing other people's copyrighted music, and that's in no way the same thing as needing a license for driving.
In the EU, Ascap would have no right to require the musicians to register their original material with Ascap before being able to perform it in public. They would also have no business to require any fees from anyone on the basis that they 'probably' would violate that promise. The license fees, IIRC were for playing music copyrighted by others. Hence the whole idea of waivers, to avoid those fees - why pay if you don't do what the license is all about in the first place, eh?
In the EU we have a slightly different situation than in the US, as far as obligatory 'union' memberships goes, I think that's the whole basis of this misunderstanding. In our view, this kind of 'union' is closer to the mob, than anything else.
In Europe we also have unions, also quite powerful, but their role is more important during negotiatons about working conditions, and presenting yourself as a group in case of disputes - not some obligatory membership without which you have no right to work.