NK had good relations with former Yugoslavia, that continued (for the lack of any real reason for hostility) when Serbia was reconstituted. The guy made, and maintained, a name for himself as a expert on military matters for decades and is tight with state security services, so was likely trusted to 'behave' through those channels. He was, according to my sources, the only foreign journalist accredited to cover the aforementioned military parade in Pyongyang. I have no doubt the North Koreans kept careful watch on him, but since he was a 'friendly' guest, they weren't as harsh as usual.
I see, was just curious why he was treated that way. Reports on NK here seem to just play up on it being under a tight grip rather than being destitute. Or at least in the past 10 years.