I assume all of this is based on FS2Open? While I love that thing (and used it myself) it has no place on this page, and should be entirely removed from game info - only recommended as a solution to problems. Unless someone released official OS X/Linux packages, in which case, source please.
Topic on Talk:FreeSpace 2
FreeSpace 2 is sold for OS X and Linux on Desura.
Ah, then that should be noted somewhere. Probably in the past tense, cause that's all going to disappear soon.