This project is abandoned and its default file will likely not work with the most recent version of Minecraft. Whether this project is out of date or its author has marked it as abandoned, this project is no longer maintained.
What Is NoDamage?
Nodamage is a plugin for use on public servers which run competitions such as spleef where players may accidentally hit each other.
Why not just use world guard and turn off pvp? or just turn off pvp on the server itself?