The title assumes North Korea did test a nuclear device, which I think likely, and not an equivalent amount of TNT, initially thought a possibility in 2006 until radioactive isotopes of krypton and xenon were detected.
There are several reasons for a North Korea to conduct a nuclear test and it’s difficult if not impossible [...]

Hillary Clinton, speaking at a graduation ceremony at Barnard College in New York City, displayed an amazing degree of naiveté:
“We have two young women journalists right now imprisoned in North Korea and you can get busy on the Internet and let the North Koreans know that we find that absolutely unacceptable,” Clinton told the [...]

The Taepo Dong 2 (TD-2) (대포동 2호) missile launch(es) North Korea likely is preparing for, and recent voiding of all political-military deals with South Korea, are part of Pyongyang’s long-term strategy of regime survival. While these actions also have less important near-terms goals – expressing displeasure with ROK President Lee Myung-bak’s relatively hard-line approach [...]

North Korea’s state media, the Korean Central News Agency (KCNA), on 30 January 2009, released statement declaring the DPRK’s unilateral withdrawal from all political and military agreements with South Korea.
Specifically cited was a 1991 agreement that included a sea border in the Yellow Sea. This signals North Korea’s dissatisfaction with ROK President [...]

NightWatch has an interesting analysis of a statement issued by North Korea yesterday, which, “carries a credible threat of incidents at sea off the west coast, but omits many of the usual terms of threat.”

In 1999 the news on North Korea was both alarmist over North Korean antics and naively hopeful of peace suddenly breaking out. A decade later the news is still often alarmist - North Korea did test a nuclear device in 2006 after all - but less naive after decade of reneging on agreements and [...]

Via the Korea Society, North Korea made the U.S. an offer it could refuse, and apparently will:
North Korea offered to send its chief nuclear negotiator to next week’s inauguration of US President-elect Barack Obama, but Washington has responded coolly, South Korean news reports said Monday.
[. . .]
“The North, through its United Nations mission office [...]

Via the AP: “Vice President Dick Cheney says North Korea helped Syria build a reactor at a site that Israel suspected of being a nuclear installation and bombed in 2007. The White House has alleged North Korean involvement before, but top Bush administration officials have said little publicly on the issue, which is still [...]

According to CNN:
The United States on Saturday removed North Korea from its list of states that sponsor terrorism, State Department spokesman Sean McCormack said.
[…]
McCormack said the United States and North Korea had reached agreement “on an number of important verification measures” of North Korea’s nuclear program.
[…]
“Every element of verification that we sought is included [...]

From Reuters: “Washington [will] not remove North Korea from a U.S. list of state sponsors of terrorism on the initial deadline of Monday. . . The [U.S.] had made clear it did not expect a deal with Pyongyang by Monday for presenting a verification plan for its nuclear programs. . .” The admin gets one [...]