AOTW,
Have a look at part 61 and you'll find for example that there is no such thing as a PPL (G) (for glider) in Australia. Yes there is a CASA issued PPL (G) but it is NOT valid for use in Australia. It is issued by CASA on request and after jumping through many hoop,s for use overseas so that Australian glider pilots can fly gliders in other countries for contests etc. Everywhere else in the world wants a government issued licence not some piece of paper issued by a private body.
In fact, as overseas authorities issue temporary permits or licences on the basis of your home country qualification (that is good for use in your home country), I doubt that this subterfuge by CASA/GFA would in fact be recognised by anyone else if they knew it wasn't valid in Australia).
I've got no problem with flying a VH registered aircraft on a CASA licence (gliders and motorgliders are VH registered aircraft) but CASA says you can't do that as they don't have the licence.This is a result of some nasty collusion between CASA and the GFA to maintain the GFA in a monopoly position. Negotiated in part by CASA officers who were GFA members. Nice, eh?
Until 2009 you could fly a glider without actually being a GFA member and there was a process in place to formally allow this in future. McCormick ordered this to cease.