I had started a thread about the Mini Gardens a while back and there was much discussion about the types of plants available. At one point during the discussion, someone mentioned the Venus Flytraps being difficult to grow and care for. That probably doesn't have anything to do with your mold issue, but I thought I'd throw it out there.
As for the mold, I'd be surprised if that is what's growing in there. Maybe you got one that wasn't sealed as well as it should be....? I got the impression that those little containers were sealed carefully and in a somewhat sterile environment at EPCOT. I was pretty scared of transplanting mine after reading the instructions about not opening it until you're reading to plant, using sterile soil and using the bag to create a greenhouse-effect. I transplanted mine (not a venus flytrap) just a couple of weeks after getting it home. It was still very small but I followed the instructions to the letter, and it did great. Still is, over a year later! (My favorite WDW souvenir!) Rinsing the gel off the roots was the most delicate, scariest part for me. I would guess that the mold (if that's what it is on yours) wouldn't hurt the plant, but I guess I'd go ahead with planting it if you're concerned. I'm no expert, just guessing and providing a little moral support! Hope it goes well for you!!