Actually, I read an article about that issue. It's not that the copyright laws are different in Japan, it's just that there's a truce present. Fandom get to profit through doujinshi and whatever-which-way while the creators turn a blind eye and ignore a few sections in the law. Because really, the doujinshi-market business is a HUGE self-sustained advertisement system that will benefit the creators and profit them more as more and more people catch word of it.

It's kind of like the fish that rides on the shark's back.

OFP = Online Fanarts Protection