If you open up the file named doomrl.ini you can change the majority of the keys. For example: To quit the game, currently you press 'Q'. If you open up doomrl.ini you'll notice a line saying:
Quit = "Q";
To change this to, let's say 'B', you would make the line say
Quit = "B";
Instead. As far as I'm aware this should work with all your possible keyboard keys. There are a few special cases like "BACKSPACE", though. I hope this helps.