You've only been scooped because they only just became available in the U.S. recently, but I have been hanging out in the Netherlands regularly for a while.
Jenever (from the word for "juniper") is a Dutch gin-like drink. The "old" and "young" designations refer to style, not to the aging of the spirit. Young (jonge) jenever is more like English gin and supposedly came into existence during WWII because grain shortages forced a change to more neutral tasting distillates. Old (oude) jenever is more like an herbal whiskey, as it's made from corn, rye, and barley. It has juniper and herbs in it as well, but the taste is more complex.
I'm quite fond of old jenever. Korenwijn is pretty much the same thing as old jenever, but there's something different about the aging or the barrels. I can't get a straight answer on this from my Dutch friends, but I prefer old jenevers that are also korenwijns. I'm thinking that the "korenwijn" (sometimes spelled "corenwyn") designation just means it's high-quality old jenever.
Don't we have some Dutch folks on here? Perhaps they can clarify.
At any rate, there's a whiskey made out in Oregon called WhipperSnapper that incorporates the techniques for making korenwijn and therefore has some korenwijn-like qualities that come through. It's light with spicy barley and rye notes. Not a heavy lifter or anything, but a great easy sipping drink. http://www.ransomspirits.com/Whipper_Snapper.php I would assume it's easy to find in Seattle, so I thought I'd give you a heads up to look for it, if you haven't tried it already.
(I also like the Old Tom gin that these guys make).