I have researched this.
It seems there was a wave of cease-and-desist letters in the 90ties.
http://en.wikipedia.org/wiki/The_Tetris_Company
The conclusion is that one can not use the word "Tetris", but one CAN provide Tetris-like games. One can use the generic term "Tetromino".
So we will have to remove the Tetris name, and replace it with Tetromino.
Is there anyone who is capable of removing any mention of Tetris in the actual game code?
I suggest a total "Replace" of all mentions of Tetris with "Tetromino", also in the image on the game.
So instead of removing it in the next update we can just replace Tetris with Tetromino.