Stealing a comedians joke is similar to stealing a developers source. I'm surprised at some of the responses here.
People like to have a laugh. Most people repeating the joke are not claiming credit for creating it. They found it funny and shared it so others could find it funny to.
I agree that most of the people are just sharing the joke, but a sizable lump of them are trying to create some kind of online brand which they use to get money.
Source code isn't written to be shared or to entertain others with. Quite the opposite, in fact, as we strive to protect source while still releasing the products built from it.
A bit of an idiotic comparison really.