regarding legality and ethics: I had a Fish and Wildlife permit to collect and raise frog and salamander eggs for some experiments I was doing a number of years ago and one of the clauses of the permit was that I couldn't release larvae back into the pond but that it was ok to release recent metamorphs to the terrestrial environment as long as I did so within 24 hours of metamorphosis. I won't speak to the legality because it really is different in every state but that clause is something to keep in mind.