In South Korea, the words are exactly the same 원수, pronounced wonsu. Not surprisingly, there is a slight difference in the pronunciation in North Korea, otherwise people might be calling Kim Il-sung and Kim Jong-il enemy. 

The pronunciation for enemy in North Korea is wonssu, written 원쑤. That slight variance in the second character is the difference between a bad insult and a title for a leader. Korean is written with spaces between words, unlike Chinese and Japanese. It also uses many of the same punctuation marks as western languages do. 

Korean is written in Hangul, the Korean alphabet, which was promoted by Sejong the Great in 1446. Before then, Chinese characters were used. Since the Korean War, huge differences in pronunciation have developed between the Korean of North Korea and the Korean spoke by people living in South Korea. Even the spelling between the two has varied greatly. Clearly, linguistics are influenced greatly by history and even by the needs of a society or government. 

(Source)