Interesting; it recognizes kills made with chainsaw, gun, shotgun, machine gun, but not rocket launcher. Plasma and BFG keys don't work.

in shareware version plasma and BFG guns aren't available

The authour could had just used FreeDoom https://freedoom.github.io

which is a free as in freedom replacement for DOOM I/II and deathmatch iWADs (totally compatible with community PWADS).