Seriously, yes. South Korea censors the North Korean websites and some illegal ones (heavy porn, for example) too. I think there are no known such instances against the free speech rather than NK-related ones, but I'm afraid that there might be in the future.
What else would they call it? (use DPRK everywhere?) They don't recognize the "other" Korea. South Korea does the same, e.g. at http://www.mofat.go.kr/