North Korea continues to bluster, making bogus "missile tests" with 1960s era Russian anti-ship missiles and threatening war if the US does not agree to a non-aggression treaty and lots of economic aid. The country is bankrupt and the communist leadership is unwilling to just merge with the South as the communist East Germans did with the wealthier free market West Germany in 1990. North Korea has not got many options. If it fires some rockets or long range artillery on Seoul (capital and largest city in South Korea), the response would probably be war and even more pressure on the starving and much oppressed North Korean population to rebel. Aid groups who have operated in North Korea report that the population is kept ignorant, terrorized and very poorly fed. Much of the food aid appears to be diverted to the military, or sales overseas. It's hard to find out. But it's not all going to the neediest populations, as the aid groups would like.

War is not really an option for the north. There is no way they could win. China and Russia would not come to their aid as they did in 1950, and American would fulfill it's treaty obligations with South Korea by supplying sufficient military force to repel North Korean invaders. 

South Koreans have other concerns about the American military. It is still believed in the South that the US would be calling all the shots in any war with North Korea, despite the fact that nearly all the ground combat troops, and most of the air support, is South Korean. Only at sea would the contribution be largely American early on. And the US could send hundreds of additional warplanes within weeks, ensuring South Korean air superiority. But it would take months to move significant American ground force reinforcements. In the meantime, the South Korean generals would be running the show. 

But many South Koreans are not sure American reinforcements would show up. South Koreans place great faith in the presence of  American infantry (from the US 2nd division) on the DMZ. Many American officials have, for decades, wanted to withdraw these troops. South Korea is an unpopular assignment for many US troops (unlike Germany, you cannot take your family to South Korea, at least not with military housing and other support.) Recent American proposals to withdraw some American troops from South Korea, or moving them away from the DMZ, makes many South Koreans nervous. This, despite the fact, that the US is unlikely to look the other way if North Korea invades again. South Korea also has a hard time believing that it's armed forces can stop the north. But for the last two decades, American military planners have understood that the north doesn't have much of a chance if they invade. The North Korean armed forces have not been able to update their equipment for several decades and cannot afford to train as much as South Korean troops do. Plus, the terrain, trenches and fortifications along the DMZ make it very difficult to attack.