See? Not everyone has to surround their creations with bristling patents, trademarks, etc:
Sudoku’s popularity in the United States caught Mr. Kaji by such surprise that he did not try to get the trademark there until it was too late. As a result, Nikoli receives no royalties from sudoku-related sales overseas by other publishers.
In hindsight, though, he now thinks that oversight was a brilliant mistake. The fact that no one controlled sudoku’s intellectual property rights let the game’s popularity grow unfettered, Mr. Kaji says. Nikoli does not plan to trademark other new games, either, in hopes this will also help them take off.
Read the article: Inside Japan’s Puzzle Palace – New York Times