This guy is finding any means necessary to add Craiglist data back into his application and Craigslist does not want him to. I think the "gray" area is pretty black and white. Craigslist said no. He's doing it anyway - even if indirectly.
Here's how I see it:
Me: Don't go in my house.
You: But you left the back door unlocked by accident, so I thought I'd just come in and eat your food.
In the real world this would not be acceptable.
Even though we are talking apples, bananas, and oranges, the same ethical perspective should be employed. Craig said no, so we respect his wishes. It's the RIGHT thing to do. If he adds an API someday, then he's sharing the key to his house with us, until then. Doors are locked, too bad, move on.