There are several different ways of getting FreeSpace.
Of course, there are still a few copies of FreeSpace 2 floating around, up for sale on eBay, or maybe lying in the bargain bin at your local computer store - although the latter's pretty doubtful. FreeSpace 2 has not been mass-produced in the United States for several years, so checking places that sell used software is your only recourse. FreeSpace, of course, has been out-of-print (so to speak) for even longer.
Get it from a friend
Oddly enough, FreeSpace 2 actually has a clause in the license agreement that states that it's legal to give a copy of FreeSpace 2 to a friend - as long as it's for noncommercial use. So, be nice to anyone who has it, and maybe they'll burn it for you.
Freespace Online Installers
Turey and [DW]-Hunter have created two installers for those who do not have the Retail version or are missing some VP or Cutscene files can use the Freespace Online Installer. Note, Retail is a requirement to install freespace open and the freespace open installer doesnt include the retail files. You will never need the CDs to play retail, This installer includes Kazan's no-cd crack that doesnt have the problems that have been occuring in the HOTU crack. As an option you can download the Freespace Open Installer at the end of the retail installation. If you have retail and you just want the Freespace Online Installer you can goto the FSOInstaller site or visit Hard-light's forum post. This is probably the easiest way and most user friendly way to get freespace2 and freespace open.But if you wish to have the cds there are many other sites you can download them from, one of the most popular sites for the cds is Hunters freespace site, FreespaceZone.
Get it from HOTU
HOTU also has FreeSpace 2 listed in their downloads. Although this download went down for a brief time in the past, it is one of the most reliable ways of getting FreeSpace 2 over the internet. Unfortunately, the version included with HOTU is stripped-down.
As of January 30th, 2006 "The game is already updated to v1.2 so there is no need to run the update." according to the readme.txt included with the HOTU version.
The Freespace Zone has .bin type images of all three CDs of FreeSpace 2 and the single CD of original FreeSpace, archived in the RAR format. The .cue files are now also included.
FreeSpace 2 is soon going to be made available via HLP's BitTorrent tracker. See the main BitTorrent article for more information about this method of distribution.
Get it from another source
There are other sources out there, that may have ISOs of the CDs, the VPs, etc. You may find some info on this thread of the HLP forums : http://www.hard-light.net/forums/index.php/topic,38195.0.html