ReactOS Tetris is a game for ReactOS initially written by David Hinz (fRy2oo5), who is now assisted by Christoph von Wittich (Christoph_vW), who mostly removes coding mistakes but also adds new features.
Current work/Todo list
At the moment the graphics engine is being rewritten and the internal functions will be restructured to avoid code duplication. After that, the score display will be replaced by a "digital" one, we will see a new "pause" screen and finally levels will be implemented.
What it looks like at the moment
Although ReactOS Tetris isn't part of ReactOS yet, it has been released under the GPL. You can get a copy of the sources at svn://reactos.dyndns.org/tetris