As I understand it, any weapons grade plutonium they have is from older reactors (i.e. pre-Clinton). The Clinton admin (through Carter) negotiated to have them stop reprocessing plutonium from those older reactors in turn for newer reactors with much less weapons potential. Those newer reactors were never completed.

While NK refrained from further reprocessing of plutonium, they were secretly working on a second method -- uranium enrichment. Thus, the Clinton deal may have bought some time with respect to plutonium reprocessing, but it did not halt the nuclear program. This is what was divilged early in the Bush admin, and why we halted completion of the reactors and fuel oil shipments, leading kim to break the seals on reprocessing, so on and so forth.