The characters don't use Interjections (exclamations) like "Fark they stole our ship!" they would just say "They stole our ship!" Also the use of slang is very rare, maybe one scene in the movie will have it a few times if there is a banter.
Now I imagine that may people love to use interjections and slang in their dialogue and that's great, I'm not trying to harsh your program. I just thought this was an interesting observation. I don't know if it really applies as much with the new movies as I read scripts form the older movies.
In instructing players who asked how to talk in character I usually say just talk like you would in D&D but without the archaic terms. That is usually a good tip and works well to stay away from modern Earth language, but with this new info I think I can dial it in even more. Do you have examples of either case of how they talk? Do you feel that underworld types who are especially uncouth might talk differently?