Just Cause 2 doesn't have a multiplayer mode—at least, not by default, it does not. But fans of the game have been undeterred and have somehow or other managed to program a multiplayer mode into the otherwise singleplayer-only game.
The game's developers Avalanche Studios have since endorsed the mod and the mod's makers are planning to release it officially on Steam, where it will soon be available. You'll be able to download the client and server files to host your very own Just Cause 2 multiplayer server to play the game with friends.
Destructoid reports that the game's final beta test will take place on December 7, with beta keys now available.
Yes, you'll need a copy of Just Cause 2 to play the mod.