To sum up your questions:
The Linux port on i.o is practically 100%, we have sound, networking, the whole lot. No music is the only missing feature besides the lack of whatever that weird match making service volition used (which nobody who uses the souce port can use). Linux port can work with mods, some of them have problems with case and such. I believe our port even works on OS X and does most of FreeSpace 1 once you add patches from kind developers on the mailing list. One of those fine people even created a special tarball with everything you need to get the B5 mod running.
Also, this is NOT THE APPROPRIATE FORUM to ask for help with the icculus.org source port, there is a a FreeSpace 2 mailing list on icculus.org, the information for it is right on the icculus.org/freespace2 website.
Not trying to be mean or anything but none of us really monitor this forum. I would very much appreciate it if anyone who is a helper (Inquisitor, etc) on this forum would remind people who ask in the future of the existance of the icculus.org freespace2 mailing list so they can get the help they need :-)