Once you're banned once, Jagex logs the users IP/mac address and (maybe some other things) and flags you. So if you create a new account, they'll be monitoring you to see if you're botting.
Tell him to change his IP/mac address don't start botting new accounts straight away.
+ You need to realise other people are also using those scripts. After a while Jagex can really tell if you're botting even if the scripts are 'randomized'