Homeworld is a real-time strategy computer game released on September 28, 1999, developed by Relic Entertainment and published by Sierra Entertainment. It was the first fully three-dimensional RTS. Homeworld was the beginning of a series, followed in 2000 with Homeworld: Cataclysm, in 2003 with Homeworld 2.
Homeworld has been released as open source via the Relic Developers network. You can download the source from HomeworldSDL