I've never had a problem with moldy DDGS because it had the solubles (syrup) added back.  The stuff should be totally dry by the time you get it, around 10-13% MC.

Now, I've seen wet DGS start to spoil after 10-14 days, but that's a different matter.

I do like DDGS with the solubles - it adds more energy in the form of fat back to the mix.  It does, unfortunately, increase the sulfur, but if the plant is doing it right, they won't over-do it.  There is a market for the solubles by itself, but I don't handle it - kind of like gasoline and matches.