I think the author means Korean in that he can't read it. I don't believe Ken Iverson had a Korean connection in making it.
The sense of "it's Greek to me". J is an extremely cool tool. We are preparing much better article about this language, which will be available very soon.
I've never heard that phrase before. Honestly it's sort of confusing.
I think the author means Korean in the sense that complicated words and phrases are constructed from a simple alphabet.