I received this game about a week ago in the recent "stamp collection" promotion.
First, I would like to say a big "thank you" to GOG for this gift - it's one of their premier products (it appears to be made by the same group that owns GOG).

My question is: How to get a censored (in particular: no nudity and no "heavily involved romance") version?

(This request might sound funny considering that most of the posts I see on these forums regarding censorship are from people who want to uncensor everything. I ask all of those people to refrain from laughing at me.)

If you want AUS censored version, just delete 2 files - succubuss.dzip and elf_flotsam.dzip.
http://www.gog.com/forum/the_witcher_2/what_triggers_getting_the_censored_version/post5

Even the censored version has some nudity, though, most glaringly at the very beginning when you wake up next to an undressed character. I've seen people replace her "dressed" character model with the "dressed in only a towel" model, though, so it may be possible to achieve the same kind of model switching to remove her nude model from the game. Of course, even then there'd be prostitutes and a topless baronness, but the prostitutes remain dressed if you don't pay them and the baronness isn't encountered at all if you spare Aryan La Valette early in the game.

As for "heavily involved romance," I'm not quite sure what you mean. There are no Bioware-ish "romances," if that's what you're worried about, though several characters have history. It's not involved so much as subtle, however, and the game really doesn't focus on it very much.

Hope that helps.

Though I haven't tried it (haven't had the game installed in quite some time), here's a mod I found that claims to remove the nudity in the beginning: http://www.nexusmods.com/witcher2/mods/43/?

Haven't found anything else like it for other scenes, though. Sorry. That's the only scene I can recall in the game where you have no option in the matter, though. It's really not a "censored version" in the sense that they went through and removed everything that could be considered offensive. It's actually just a version designed to permit sale of the game in Australia because the government there disallowed things like sex as a quest reward and wouldn't allow the game to be sold unless the two offending scenes were removed from the game.