There are fan-made rulesets under the same name, usually due to a similar scale. I've played the Heralds of Ruin rules, and they are good fun. Not sure if you'd get away with using them in a
GW store, though.
http://heralds-of-ruin.blogspot.ca/p/kill-team-rules.html
You still need the
GW rulebook and respective codice to play, but the rules are intuitive and the game enjoyable.