retrogames: You can play with the mouse, but navigation is awkward. My keyboard has a compact design, and doesn't have a numeric keypad. I looked on Amazon and discovered that you can buy USB numeric keypads. I wonder if this will work? Does anyone know? Thanks a lot.
Arkose: You can use the DOSBox mapper (Ctrl+F1) to remap the keys however you want them. If the key you want to use already has a mapping you can go to it as well and repeat the process to move it to something else.
Number pad 8, 4, 5, 6 are forward/backward and turn left/right, 7 and 9 turn left/right while moving forward, 1 and 3 are strafe left/right.
Thanks a lot. I didn't realise I had a reply for my question, because I received no email from gog about it. Pity, because I bought a numeric keypad. It worked, but I will now investigate DOSBox's mapper...
Edit. DOSBox mapper worked well, thanks.