Freespace 2 is considered to be one of the greatest space sims of all time. When the source code to the game was released the community set to work at updating the game engine. The result is the Freespace Source Code Project (or SCP) which updates graphics, sound, and other minor tweaks for the game. (And also makes the game available to Linux and Mac players.)
The music playing in the background is "Shame" by Stabbing Westward.
More information on the Freespace games can be found on Wikipedia:http://en.wikipedia.org/wiki/Descent:_FreeSpace