Sorry, but taking an outdoor cat is probably a crime.

I'm working on some research over the summer about lost and abandoned pets, so this video from Slate's "Dear Prudence" advice column was particularly on-point.  While I agree with Prudence's advice to take the cat, the advice is illegal.  The cat is not abandoned unless the neighbor intended to abandon the cat -- a fact compatible with but not suggested by the original question.  Thus, taking the cat would probably subject the taker to civil and criminal liability.  And Prudence would probably be found to be aiding and abetting the crime of theft.