I just so happened to hear Duff talk about it on one of his episodes....He said it doesn't get tried out like fondant? Maybe it's a fondant/GP mix?
Maybe he meant fondarific, I tried their sample pack and it did dry out, but stayed pliable for a really long time. And it was super stretchy, I kind of like it, but it's not as smooth and opaque "creamy" as satin ice. It also tastes awesome, the flavors are pretty strong. It reminds me of a soft Airheads taffy.
Duff was talking about "Fondarific." You can order an inexpensive sample pack from them. http://www.fondarific.com/
Their buttercream flavored fondant is really yummy. I thought the fruit ones were pretty gross, though.
If it was a fondant/GP mix, it would get rock hard pretty quickly. Gumpaste is a type of sugar dough that dries very hard, very quickly.