Need help for developing / editing plugins

Hey everyone,
i want to edit some Plugins for my Server, but I have some problems to do that, caused i'm not firm in developing plugins and need more informations about the including of library's, using script-commands and so on.
For your understanding:
I downloaded the Plugin "BountyBoard" (.js) from oxidemod.org. Now i found an exploit for others. Some Players can get the amount of the bounty set on their friend by simple killing them.
To avoid that exploid i tried to integrate an if-order to prove if the attacker is an friend of the victim.
I've read some codes from other plugins, especially the RustIO:Template Plugin.
There is an function to do, what i want so much. But i cannot use it. I think it's caused by the missing library Integration.
Can you help me, to get started in developing some cool plugins for Rust/Oxide ?
It's btw. Rust Experimental.

I've uploaded the scriptcode edited by me. Hopefully it Shows how i want to do.

I would very appreciate an answer from you
PS.: Sorry for my english :/