KI23, from experience with dart frogs I can tell you that GE 100% silicone (after it completely dries) is safe for animals, just make sure it doesn't have any "anti-mold agents" or stuff like that. I've not heard of coco fiber going moldy in a normal use situation, that's one of its benefits. Dart frog habitats are usually kept just as wet, if not more, than chameleons and they're really sensitive little critters. Lots of folks in that hobby use the coco-over-brown-silicone trick for backgrounds.
That said, I'd love to see an update from Banksy! I've started making my own custom cage and wish I had seen his first, refinishing a cabinet would've been much cheaper, easier, and better looking than going from scratch like I'm attempting!