Hello fellow pilots,
I repost here a reply on a ticket for errors on running the game under GNU/Linux. It's was tested and working under Ubuntu and Debian. It's actually a copy of the wineprefix elements generating the windows environment for the game to play.
So here's how to make it work:
1. Install playonlinux on your rig. I am currently using version 4.3.4
2. Create a new virtual drive from the PlayonLinux configuration menu, 32bit windows installation, 3.0.2 wine version.
3. Download this and this(I have split the archive in 2 for size reasons), unpack in a temp folder.
4. Replace the files extracted in the wineprefix you have previously created(EDIT: it's under /home/"your account name"/.PlayOnLinux/wineprefix/). They will replace the config files and the drive_c folder entirely.
5. Now restart PlayonLinux.
6. Install a new, non-listed program in PlayonLinux, to create the shortcut for the game. Select edit or update an existing application, then check the box "show virtual drives", select the drive you created previously, click next on the proposed things to do before installation, choose a 32bit windows installation, pick an exe file from the drive ( I recommend ../.Playonlinux/wineprefix/"yourdrive"/drive_c/Program Files/Freelancer/EXE/Freelancer.exe). At this point the game will start, but the shortcut isn't yet created, so close the game. Then select the Freelancer.exe again for the shortcut to be created. Cancel the process if you don't need other shortcuts for other applications from the same drive. Or add also FLModManager, if you think it's useful, the app is there.
7. Run the new shortcut, to test the game. I created an "It_Works" character, just to test if the game works and connects properly to the 24/7 SWAT Crossfire Role Play Server.
8. Configure PlayonLinux, select your virtual drive, click on the Wine menu, on the right tab, start the Registry editor, and search for Freelancer. Under \HKEY_CURRENT_USER\Software\Microsoft\Microsoft Games\Freelancer\1.0 you will find the MPAccount name and the MPAccountNamesig. If you need to set up a new player, delete the 2 keys, they will be recreated the first time you start Freelancer in MultiPlayer.
9. If you already have a MP Account, there's the place to fill in the data about it.
10. Happily play Freelancer Crossfire 2, thanking the developer of the mod for his great work!
Good luck and let me know if it works for you 
Dan
PS: @(IOC) Wanderer suggests that you could also do the following, in your installed wineprefix:
"Оne can reduce game size a bit more by uninstalling FLMM and deleting all .flmmbak files. It is unnecessary to keep them after Crossfire is activated, because deactivation will not be possible anyway (it's an old problem with the Crossifre mod).
For even more space saving on my system, I also renamed _blank.wmv to swat.wmv in DATA\MOVIES and removed all other files in that folder. The game is still fully functional, but now occupies only 6.28 GB (4.02 GB on disk with NTFS compression). You can do the same if you don't need the startup movie.
Hope this helps!"
