According to Mother Earth News you need to dry them, although it's probably that you can dry them in the sun or the dark!:
Butternut trees bear early-at just two or three years of age. The fruit is elliptical, like a long, narrow egg, and has a thin, green outer husk covered with fine, bristly hairs that give off a near-permanent brown dye. The inner surface of the husk produces an equally powerful orange dye. (Time to get out the old clothes and rubber gloves again.) The nut inside is oval, with a deeply ridged and pitted shell that's almost but not quite as difficult as 1. nigra to crack.
The thin, fragrant, oily kernel inside each shell can go rancid quickly, so it's important to shell and use butternuts soon after you've husked and dried them. No problem; butternuts are sweet and delicious straight from the shell, raw or roasted, or baked in cake or pastry.
Here's the whole article ("A Fall Field Guide to Nuts"): http://www.motherearthnews.com/Natur...ts.aspx?page=5
Wish I could help -- we have no butternuts but are on our way out to harvest hickory nuts -- the kids & I foraged 10 lbs of nuts (after hulls removed, although most were just sitting on the ground!) A heavy rain and some wind this weekend and it's raining hickory nuts here!