Vassal is a game engine for building and playing online adaptations of board games and card games. Play live on the Internet or by email. Vassal runs on all platforms, and is free, open-source software. This software requires java to run.
If you like this software please consider making a donation to the authors at their Official Site
There are hundreds of games (mods) made with this engine to play!
Here is the link for Vassal 40k