The reason is clear. They have a history of suing Namco over Namco's own copyright that they hacked up in a garage and somehow winning, including just a few years ago over the reunion game. Probably the only way they won that one is because of the agreement reached in the lawsuit in the early 80's which they clearly should not have won. Imagine if the same thing happened today and someone hacked up World of Warcraft into World of CrazyCraft and started selling it. It's ridiculous. Anyway, since the reunion suit, Namco has been sending out cease letters to anyone who infringes on Pac-Man and of course they would probably like revenge on GCC at this point. It's really their own fault in a way, they were too lazy to keep fighting over it in the early 80's.