I've taken a look at some of the extracted files. App World is updated at a version 188.8.131.52, and MSN is at 2.5.83. Also, there seems to be Slacker Radio built-in to this OS, looking good so far.
I tried to update App World, but I got a 907 error...looks like people on OS 5 won't be able to use it anytime soon. Maybe someone using OS6 could try it?
Heres the link:
Just unzip, place the folder in your phone, then browse to that folder and click on the appworld.jad.