Re: separate sections for non-English discussions (eg: Japanese).
AO is an English site for Japanese interests, and I think it should stay that way. An occasional Japanese discussion is fine, but if you want to talk in Japanese, there are better places to do that. I'm not sure many Japanese would even get involved with AO if a Japanese-only subforum was created; the dynamic of discussions between username- and anonymous-style boards is just too different, and I think most Japanese would simply stick to 2ch. We'd simply end up with a few Japanese users, plus those of us who can speak Japanese, and that would become our AO Japanese clique.
That said, I think the FAQ should provide an introduction to AO, a quick tutorial on how to sign up, how to participate in discussions, how to manage an account (eg whether post count matters), and perhaps names of some volunteers who can handle non-English questions via PM in the event they're having trouble with English. That way if a non-English speaker wants to get involved with the forum, they don't have to feel intimidated.
Another way to think about it: try visiting a forum like copycat2u (if you can't read Chinese). What do you find frustrating about navigating the forum? What kind of information would help you find topics you're interested in, and would help you understand how to join in the discussion?
Re: 4chan and copyrighted material.
The reason 4chan hasn't been shut down is simply because their servers don't actually host copyrighted material. Almost all of it is linked to rapidshare/megaupload/etc. Therefore it has been the responsibility of copyright holders to file takedown notices directly with RS/MU/etc. And as long as users aren't careless about their HTTP-referrer headers, it's pretty difficult for filehosts like RS/MU to track down the referring website -- especially when threads on boards like /b/ expire at a very fast pace.
Torrents receive much more legal scrutiny because copyright holders can't file takedown notices (eg: there is no single server that hosts the files). Moreover, the high profile cases are with music and movies; hentai/VN/Japan-centric content is small fish, and most Japanese companies don't even sell their products outside of Japan for it to be worth their time/money to pursue heavy legal action.