Pioneer started off life as a basic spiritual successor to Frontier: Elite II and nowadays it continues being upgraded, to give fans of classic 3D space exploration something fun.
Pioneer is another classic example of a long-running free and open source game doing well, with a brand new release up that overhauls plenty of important parts.
Inspired by the classic Frontier: Elite II, Pioneer is a free and open source space adventure sim. Open-ended exploration, allowing you to do whatever you want and there's a big release out now.