This is a cross-platform (java) version of the classic chinese game Mah-Jong - it is not the solitaire tile-matching game. The game is for 1 human player vs 3 AI players, is based on the British & Chinese versions, supports all the standard Special Hands, and has many configuration options to make the game play how you like it.
There are two installers available - one for Windows (an executable) and one (an executable jar file) for any OS supporting java 6 - which should include Linux & Mac. Java 6 (or above) is required - this can be obtained from http://java.sun.com/javase/downloads/index.jsp if you do not have it already.
The installers can be downloaded from here