There is a protection. I tried this script - it works fine.
http://svn.navi.cx/misc/trunk/python...sey_patcher.py
I instaled nasm and active python in order to execute the script.
You need to patch GAME.EXE, LAB.EXE and TUT.EXE.
See the comments in the code of the script for details.
(I chose command line options -k -r 20 -f and it works fine on DOSBox)