The rules are the same as Conway's Game of Life, but there are two competing forms of life. They don't hunt each other, but they do compete for resources.
The game will start with a 'big bang'. 20% of the squares will spawn a blue cell, 20% will spawn a red cell, and the rest will remain empty. Life is allowed to run for 100 generations, after which the player with the fewest cells begins by playing a number of cells equal to the difference between the two players' cell counts. After that, each player takes turns spawning a number of cells dictated by the number of currently living cells and the length of the current game.
You can build the code yourself with GameMaker Studio 2, or you can use one of the included installers.
Download and run gameofdeath.exe
Download and install gameofdeath.dmg
tar xzf gameofdeath.tar.gz
cd gameofdeath
./gameofdeath.sh