This certainly is quite a dilemma.

I am in agreement with PAYITFORWARD, but as an indoor\outdoor kitty owner, I would never allow a kitten to be outside, that is just plain DUMB.

To take the kitten would in fact be stealing, as I see it, and I don't know the laws in U.S.A, but here I am sure you could take someone to small claims court in order to get the kitten back, if that is what they wished to do.

However, leaving it, knowing its outside, and that it more than likely will be squashed by a car or eaten by some predator seems inhumane as well , its kinda a catch 22 situation.

What was the owner's response to your comments,?

Honestly I am unsure as to what I would do in these circumstances, I would be torn as to which is the right thing.

Perhaps talking with the owners more would be a sensible thing to do, and if you do decide to take the kitten, well good luck and don't leave your decision for too long , or it may be too late.