I really like SAGA so far, its a great game. Now if only somebody would make worthy sequel to Privateer to.
http://vegastrike.sourceforge.net/
Vegastrike is unique but strongly inspired by Privateer(as the main human faction being called Confed isn't obvious enough).
The creators of WCS also had a project on this open-source engine:
http://privateer.sourceforge.net/
I suspect they gave up on it and decided to focus on WCS instead, although the boards in that project are still active. Vegastrike is also strongly inspired by Privateer although it is very different. First because of a fully newtonian flight model. Second because capital ships in it are balanced in a way that they are much, much tougher to defeat and by all accounts space fighters will never put even a dent on them. Third because you can fit beam weapons on fighters and finally, most important of all, because it already got an alpha multiplayer persistent world mode on and a working server for trying it.
The bad news is that although already playable Vegastrike is far from finished, and from the pace of development, there are many thursdays left yet. Also joystick is pretty much mandatory for it unless you start up as a trader until you make enough money to install the auto aim upgrade on all gun mounts because its mouse control is very crude, and according to some its controls as a whole aren't stellar due to poor sensitivity. It is closer to I-War 2 because of the full newtonian physics, except for being far less polished of course.
As for WCS
Damn, I got stuck in a mission where you are supposed to attack several transports about to dock in a space station with a heavy fighter and no escorts because all escorts got wiped out by stealth fighters and I just don't like the "skip mission" or "lower difficulty" suggestions. Ignoring the enemy fighters to go straight for the transports is suicidal past the first transport you can take down with a torpedo, but shooting at the fighters will only spawn more of them and besides that you can't let more than one of them to successfully dock. destroying transports using only guns while faster fighters keeping spawning, add to that the fact the heavy fighter is the shittiest space fighter in the entire game.
Once I did it, but then I had tons of fighters after mine, the retarded AI allies doing nothing to help, all countermeasures depleted and suddenly several missiles homing.
And then the afterburner ran out and you can imagine the rest...