I agree with you completly, Teletoon most likely just made a mistake, I've heard they do that a lot. Same with that new game on teletoon, they could have just made a mistake when they made it, it doesn't gaurentee anything.. DJ's in TDA, Courtney's not, at least at first, it's very possible she might come back later. But Courtney's not replacing DJ.

Just because her voice actress is working, doesn't mean Courtney's going to be contestant. It's very possible that she's just going to be seen on the side lines, and talk a lot more then the other non TDA campers. There's still the possibility that she's going to try and break onto the set a lot during the season. Unless the creators specifically say that "Courtney's going to be a contestant in TDA", then there isn't any official proof that Courtney's returning as a contestant, but she is going to be seen.