After a combined effort of around 3 hours (hex editing, debugging, finding a computer with two monitors), I've finally figured out the password for Robbie's textures.zip file. Guess what it is?
The password is 1.
I guess I think game developers are too smart. Maybe they are, if it takes me 3 hours to find out one character.
Robbie's face is jeering at me from the game's icon.