It is multiplayer, but also has open single player available for you to play around with.
Chat with our AI personalities
If you download Freelancer Mod Manager (FLMM), you will get a few basic mods to begin with. One mod included with FLMM is a battleship mod. Alternatively, you can download the many popular near total conversion mods which give you quite a few difficult and crazy battleship missions (Discovery, TNG, Crossfire and Tekagi's Treasure come to mind).
install the aether mod
It is not possible unless you download the single player command mod.
Try a mod. You could use InvEdit or SPC (Single Player Commands).
It does. It should work with a lot of other mods as well.