I remember playing the shareware version to death back on my Win98 computer, however that was with the directional keys and ALT for strafing. That doesn't work too well anymore.
Does the GOG version have WASD + mouse control?
i will purchase this the second I get a confirmation!

W is a reserved key. It does a 180 degree turn and can't be changed in the in-game options. Similarly Q and E are used for 90 degree turns left and right respectively. You could set up another set of keys. You will have to experiment to find ones it won't refuse though.
There is also mouse control.

mark a post as solution then :)
else the system will think it is unresolved