Lucky I still remember my password.
But yeah.. considering this is a really old script, I'm not really sure if it properly works for the newer mirc versions.
I cant really check since I havent used mirc in like 5+ years.
There is also a b2 of the script here -> http://www.hawkee.com/snippet/334/ <-- iirc, it has some fixes and also has !3v3, !4v4, !5v5 and !6v6 commands.
If the script does indeed still work, an op should just have to write !on and then any user can !add or !rem, gonna install mirc on laptop and see if there's an issue.

Edit: Ok, I downloaded the latest mirc. Loaded the script and it seems to work fine. After you load it and enter a channel, you need to right click in the channel -> Gather Bot -> Set Channel - and write down your channel. Then just read the help for the basic commands.