Jobs responded to that case at D8 conference. He said it was a mistake ("We had a rule: you can't defame people. We thought it was sane to have such a rule, but the problem is that political cartoons, by definition, defame politicians. So, we made an exception for political cartoons") and they soon changed their guidelines to let the app in, but the developer never bothered to re-submit the app.
That app isn't defamatory though. Caricature isn't defamatory without associated symbolism or represented actions to make claims about the individual represented. Drawing a silly picture isn't enough, you would have to draw a picture of someone doing something negative that they do not do, in a way that implies to the viewer that this person really does this thing and that you are not just joking about it.
