Lisa, how does a poisonous dart frog administer the wound? I wasn't quite clear on your description. Do you mean that if the poison touches an open wound it will infect your blood stream by that means? From what I've read and heard, the consensus is, that if it is injected from an animal it is called venom(which, ofcoarse, is poisonous). The definition posted does describe venom as poison but poison is not described as venom in the dictionary (Oxford English). Even synonymous words don't always mean "exactly" the same thing. Some apply more to certain situations then others and that is how I see it in this case.
The origin of the word venom is not venous, but they share the same stem and thus are derived from the same origin.
vena -ae f. [a blood-vessel , vein, artery; a water-course; a vein of metal; a vein of talent, disposition, natural inclination].
venenifer -fera -ferum [poisonous].
As for toad venom, perhaps any poison coming from an animal or living thing is considered venom. Looking at the origin it doesn't seem to make sense though. Perhaps its just the simple fact that many people use these two synonymous words interchangeably without knowing their origins. The origin is in fact, the root of the definition.