If you watch the trailer, "Len" basically says the original line: "If you contract with that Dragon...you'll get vented." So obviously they are keeping that concept.
Also there aren't really, to my knowledge, any actual "swear words" in the Japanese language. There are taboo words, perhaps, but what you mainly see in fan-subs are various iterations and, sometimes oddly chosen, translations of words or phrases used in various levels of "rudeness." The most commonly seen being harsh levels of "You!" better translated as "You jerk!" or in formal cases "You cur!". Contrary to popular belief, some subbed anime and toku are alot less "adult" then fansubs (often made by more adult fans) would make them appear.