http://vegastrike.sourceforge.net/
https://en.wikipedia.org/wiki/Vega_Strike
http://www.moddb.com/games/vega-strike

Vega Strike is a first-person space trading and combat simulator, developed for Microsoft Windows,
POSIX Unix-like operating systems such as Linux, FreeBSD and Mac OS X systems.
Many of the core game mechanics of Vega Strike are indirectly inspired by Elite.
The successors to Elite, namely Wing Commander: Privateer, were particularly strong influences.
Released under the GNU General Public License, Vega Strike is free and open source software.
See above links for more inclusive details.

PS: Privateer Gemini Gold also available.