The Tribes Universe website now offers free downloads of many of the games in the Starsiege and TRIBES series, from 1994's Earthsiege through 2012's free-to-play Tribes Ascend and much of what came between, including the classic shooter Starsiege TRIBES. With most of the Tribes series being multiplayer focused, it may be hard to find games, but the free releases may influence that. There's a thread on reddit about this that includes instructions on how to get the older games running using DOSBox and other tools. Thanks PC Invasion.