I found an interesting Perl script called extractnrg which is able to extract tracks from Nero 5 images and generate cdrdao .toc files for burning under Linux.
I've tested it with some Nero 5-made .nrg's and confirmed it works. It's not quite where i want to be, but it gives me the most vital piece of info needed to make NeroRip a reality: an understanding of the file format itself.
P.S. if anyone has information on the image layout used in Nero 6, it would be greatly appreciated.
a new version of CDIRip has been released ( the first by me ) with some key bug fixes. Now properly support DJ 4.0 made images, as well as v2.0, v3.0, and v3.5!!