Librelancer
Librelancer is a cross-platform, open source game engine re-implementing the 2003 space trading and combat game Freelancer. The engine comes with an editor for several of the game's file formats called LancerEdit.

NOTE: Playing Freelancer with this engine still requires the Freelancer data files that you own.

Currently, the engine is not yet capable of playing through Freelancer properly. However, steady progress is being made in reverse-engineering the game and re-implementing its behaviours.

Librelancer requires a video card supporting OpenGL 3.2 minimum. The engine may be run on both Windows 7+ and any modern Linux distribution supporting Mono.