This is interesting. I always loved iTunes 4. I feel it was the last pure version of iTunes that wasn’t bloated and actually ran well on everything.
What OS are you running with iTunes 4.0? Officially, it was only supported on Jaguar
(according to Wikipedia). Obviously you’re on a themed Tiger or Leopard. How did you coax it to install? And assuming this is Tiger, would it be possible to run it on Leopard, too?
On my server, it's 10.4.11 Tiger server.
My Quad G5 is running Leopard. My 17" PB, which is in the pic above is also running Leopard. Both 10.5.8.
Originally, I downloaded it from a public FTP site from a university in Australia. No install, just unzipped and opened.
You can get it direct off my Dropbox:
https://www.dropbox.com/s/2hmag72m6p9hvt6/iTunes 4.0.app.zip?dl=0
Keep in mind, if you have any existing iTunes database you want to move it before opening this. Anything you want in 4.0 you'll need to redrop into it. And do NOT open another version of iTunes after 4.0 because it will update the database automatically and you'll have to start over.
Lastly, only 4.0 is streamable over the internet. That's why I am using this specific version. 4.0.1 killed this. Also, as I mentioned in earlier posts you'll need to open ports and forward them if you want to access from the outside.
Sorry if I am repeating myself.