It is my understanding that the web client is identical for both Pay-Pandora and Free-Pandora.

The ways to skirt this may include using X11 to access Pandora in Chrome or Firefox (with Gnash or an updated Adobe Flash) on a remote Linux box, or Remote Desktop Connection to access it on Windows, or to use a mobile device like an iPod Touch to stream Pandora. You could use a line cable to pipe it through your G4.