I now have iTunes library sharing working in Linux, thanks to this article at O’Reilly network. Although the article refers to Ubuntu Linux, I was able to install mt-daapd and howl easily in Debian.
I back up my home directory on the PowerBook to the Linux box, so I pointed mt-daapd to the backup of my iTunes Music folder. The linux box shows up as another source in iTunes, and it even streams my protected AAC files from iTunes Music Store.