IoM was in GPL and NR2003, too. Targa Floria is in GPL and rF. Haven't tried Trento yet, but I also don't yet have my hands on a copy of nKPro... might still pay for it, I did like the demo, and I'd like some more playgrounds...
Personally, I love the ring. Partly because of its infamous reputation, partly because of its insane speed, partly because of the scenery but mostly for the variety of challenging corners and elevation changes. Just a wonderful circuit to drive in a game, and I'd imagine in real life, too.