What a strange article. It took the WMD element and used it to completely bash Bush anyway. A couple things...
The justification for war was not simply that he had an ongoing chemical weapons program. It was that he was misleading investigators, hiding munitions, had an ongoing chemical weapons program, and that the weapons may fall into the hands of bad guys. This story verifies the first two (which we knew already, although not to the extent of 5000 weapons and the stockpiles indicated), and then openly frets about the 4th at the end. The difference is that back then we feared he may sell what he had to bad guys and now we fear the bad guys will simply take them.
The article confirms hidden stockpiles. In some cases, they were mislabeled (a common practice to deceive, per the article), and in some cases they were hidden and buried (also common practice). It also appears they were sometimes simply lost in the shuffle.
They were not inert or useless as RJ claims. Many were, but even the crappy ones were able to cause damage to our troops. In some cases-- and probably more cases than we know-- they were used as IEDs.
The US connection here is a bit exaggerated and I think it is offered up as an explanation as to why they weren't divulged. I don't buy it. A chemical used in the creation of mustard gas was purchased from two US companies in the 80s and some used a US weapon design for delivery. Big whoop. I wouldn't expect the Iraqis to design their own delivery system from scratch and the chemical in question is commonly used in other products, hence the fact that it was even available for sale in the first place. It does, however, seem plausible that the larger European connection may have been enough to keep these reports hidden.
Overall and from history's standpoint, I don't think it moves the needle much either way regarding the decision to invade Iraq. Maybe a bit more in Bush's favor, but not much. Disbanding the Iraqi army did a lot more damage than anything else, and that can't be changed or "discovered" at this juncture.