I think you may have been misinformed. It is perfectly possible to play SSE without an internet connection with the 'regular' VStep boxed edition.
(Steam requires an internet connection because all Steam games do.)
However, without an internet connection there would be restrictions:
You would not be able to play in Multiplayer
Not able to directly download and apply updates
You would not be able to download certain missions, nor download DLC's
DLC's are
Down
Loadable
Content, such as extra ships etc. Nice, but not necessary.
Many of us are eagerly awaiting (for some time now
) an update of SSE.
I don't really know if it would be possible to download this (or other updates) via an E-mail link onto a USB-stick or DVD to transfer later onto your other computer. Perhaps someone else can tell you more about this
Anyway, you can buy the 'regular' boxed version of SSE here:
http://www.shipsim.com/products/shipsimulatorextremes
regards, salty