Largely, North Korea remained neutral to the Soviet-Afghan War, though they certainly didn't appreciate both China and USSR's involvement.

1. North Korea was balancing itself between China and the Soviet Union as the international communist solidarity broke down in the then-ongoing Sino-Soviet split. China's rapprochement to the U.S. in 72 was seen as a kind of betrayal so when the invasion happened in 79, I think it is fair to say that NK was leaning more towards the Soviets (not to mention NK was still largely dependent from material goods from the Soviets during this time.
2. However, North Korea during this time was also trying to carve out a third way in the Sino-Soviet split. It was trying to present itself in the 60's and 70's as a model country for third world countries especially in Africa and the Middle East (Latin America remained rather strongly pro-US and East Europe was under Soviet control). It was trying to sell its Juche ideology (which I have to add is a bizarre thing in itself but not very important for this post) and gain support among third world countries and the Non Aligned Movement by extension as a way of gaining legitimacy in the international stage. By the late 70's, it was starting to become more obvious that South Korea was winning in the inter-Korean competition due to their growing economic advantage, but North Korea still relatively had the upper hand in the battled for legitimacy in the United Nations for the time being due to their support among third world countries, especially in Africa, in addition to communist nations which North Korea (I would dare to say masterfully) balanced between Chinese-aligned, Soviet-aligned, and the more independent communist nations like Albania and Yugoslavia.

As a result of these factors, North Korea would have liked everyone to stay out of Afghanistan, but ultimately, they could not do anything because politically their hands were tied.