Ok mate, I'll try and explain best I can. All scripts are are files which perform certain tasks for you in game. They can perform certain tasks such as bunnyhopping by the script telling the game to "jump, turn left, jump, turn right" etcetc.
They are NOT against VAC rules, you cannot get banned for them as they cannot particularly benefit in normal games, as they cant help your shooting etc.
I don't know why ZfH rules say you cant use, cus they dont really do much, but whatever.
You can't really tell who's using them, but they aren't illegal so who really cares.