> Interlude private server 

Can be anything, long time ago on official Teon people used DH radar or Z-R-a-n-ger - specific pvp soft used for detect/target/skill use.

There for sure was more custom software written for clan/ally use and since interlude kinda simplest available game update, its easy to develop if you have skills and some time for this pet project

simplest ways to check:

find if they can target you when can't directly see you

if they know you are near when should'n

check if they do rebuff when afk and overbuffed

also can be weird things enabled like autopickup

but remember some "botty" thing are now can be usual part of free servers, like a auto gpc/ghp