Complex sentence: Decision Games is a wargaming company, founded by Christopher Cummins, that publishes Strategy & Tactics magazine and appears to have bought most of the rights to many Simulations Publications games and is reprinting many of them, as well as creating new games.
Split into simpler sentences: Decision Games is a wargaming company, founded by Christopher Cummins, that publishes Strategy & Tactics magazine. The company has bought the rights to many Simulations Publications games and is reprinting many of them, as well as creating new games.