Please, change tooltip on connect to QWfwd.
Now its:
"prx userinfo key is not set"
- clueless for almost any man, that want use proxy like older qizmo or cheapo.

Change to something like:
"To use this proxy, type /cl_proxyaddr <get_public_address_of_QWFWD> and then connect normally"
"or upgrade your client at ezquake.sf.net if command is not supported"

Time to green world

Perhaps the client could be changed that when it connects to a server about which it realizes is a proxy, it will disconnect and set/change/append it in cl_proxyaddr.

Good idea!
But i mean guys, that not played some years and cant understand what to do with that message

Both is good

Is it possible to get this to work with GLQuakeWorld for Mac OS X? If so how?

The command /cl_proxyaddr is not recognized by my client.

Thanks.

Use ezQuake for Mac OSX instead of GLQuakeWorld