Is there a keyboard command? I just use CTL-Alt-Del for now but I'm sure there is a way in the game.
Actually, there isn't, as far as I can tell. The game is so old that one would actually power off their computer when done playing. The way I quit is to simply quit DOSBox. You can probably do this by pressing ALT+F4, or you can switch to windowed mode by pressing ALT+ENTER and then click the X in the top right corner of the window.