Maple should be safe. Again, if you have a species that doesn't tend to chew on leaves you have more options for plants. I don't know if a maple will get enough light in a cage setup or not.
Maple is safe, but requires a cool rest, so it will not do well longterm in a chameleon cage. If it grows outdoors, locally, up to and below zone 8, most things will need a cold Winter period you can't provide in s chameleon cage.