A fortwars server with any system that disallows you from killing people is bound to will fail.
Looks like he was searching for a way to abuse.
We have a thread for this already.
I think my Fortwars is the only one that has really worked out in this sense. I never needed a no buildkilling rule because I made a script to separate the builders and fighters.
But what is the point of not letting people kill builders?
So they can, y'know, build a fort.
But how is it challenging if they can't die?