It should surprise nobody by now that the languages spoken in North Korea and South Korea are not the same. The two countries have been geographically separated for decades, with no free communication allowed across the border between them. In addition to that, North Korea's government initiated purges of the language long ago to get rid of foreign words or borrowings (from English, Chinese, or Japanese) and replace them with pure Korean translations. As a result, while South Koreans might want to eat 아이스크림 ("ice cream", transliterated) on a hot summer day, a North Korean will dream instead of 얼음과자 ("ice snack").
When I visited North Korea last year, I found myself unable to understand much of the Korean that I heard being spoken. Of course, my Korean listening comprehension level is fairly low, but it wasn't just me -- even the Korean-Americans in my tour group who were fluent in (South) Korean had some difficulties. Most of it was due to the differences in vocabulary, but there was also the intonation of North Korean, which would have been considered a mere dialectal difference back when Korea was unified, but is now one of the markers of the two languages' divergence. (The line between "language" and "dialect" is a fairly blurry one, even for linguists.)
Anyway, when I came across this advertisement/PSA for a new app called 글동무 ("classmate"). I like the name -- the whole phrase means "classmate", which directly references the app's usefulness for North Korean students struggling to keep up in South Korean classrooms, and encourages a camaraderie among youth. Also, the first word (글) on its own means "writing" or "knowledge". The second part (동무) on its own can also mean "comrade", but I don't think that was intentional.
I have taught camps and tutored students from North Korea in South Korea before, and I can say that an app like this would be very helpful for most of them. (For others, especially younger students who basically grew up in China while their families were in hiding, it would perhaps be less useful than a Chinese-Korean dictionary, but those already exist.)
And in addition to the app's usefulness, its beautiful, simple design and hi-tech programming (it can use the phone's camera to identify unknown words automatically and offer translations immediately) are really compelling. This amazing app is the brainchild of linguists, computer programmers, and sociologists who saw a need in South Korea and came up with an elegant solution. I hope that the work I will do in the future can be as beneficial as this!