I know that Korean inc 'H2 interactive' did translate in Korean at ARMA 3 Package(not steam). It's also clearly visible when we type Korean and also greatfully work in subtitle. but when we start to type Korean the game make a short blink and some computer's FPS going down. or fixed in 30fps. or even it makes crash or freezing (not sure different language in one server make crash).
As I request to put Korean translation in VAS Addons. Modder said the game engine didn't support Korean language. If you guys can fix this please fix it :(

and also can't tpye latter like this (don't know you guys can see this latters)

ㄱ ㄴ ㄷ ㄹ ㅁ ㅂ ㅅ ㅇ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ

It just showed in blank and can't write of them

and some how it didn't typed right

if I type like this

서쪽에 적 발견

It's typed like this

서쪽에 적 발

As you can see it didn't show all of sentence, if we want to show full sentese, we have to press spacebar before type and enter

I strongly recommand to contact 'H2 Interactive' and give or help them to make korean language to right place

I'm sad to heard when VAS Modder said that arma 3 engine didn't support Korean language :(