I have not attended a class like this, but to me it is sounding like they are saying that basically if you attend the show, they can use your name, picture, etc in advertising, flyers, letters, etc.
Usually, there are pictures of shows on flyers for advertising, and for articles afterwards and since those are used everywhere, that is where the world wide part comes in.
At least that would be the way I take it. I don't take it as if you design something while in the class it is theirs. I take it as information about who attends the class.
Having given my opinion, I have not attended a class and have not been required to sign one of these. Please wait for other's opinions who have this experience.