I know nothing about Supreme Commander except what I've read in the
last few minutes. But I have picked up that there may be different
versions for different operating systems. One version runs on Steam,
[1] which is supported on Windows, OS X, and Linux.
<https://en.wikipedia.org/wiki/Steam_(software)>. I also hit info
saying that Supreme Commander runs on both Windows and XBox 360.
I also know very little about Steam, but if you're wanting to extend
the Steam version, the Supreme Commander API reference [3] might be a
good place to start. You might also need to take a look at the Steam
API [4].
But you might consider waiting until you hear from someone who knows
way more than I do about Lua and games. There's no shortage of that
kind of people on this list.
Best regards,
Paul
[1] <http://store.steampowered.com/app/9350/>.]
[2] <https://en.wikipedia.org/wiki/Steam_(software)>.
[3] <http://supcom.wikia.com/wiki/Lua>
[4] Search for steam api. That produced several different steam API
references but I suspect you'll find a more integrated resource once
you register and get inside steam at
<https://steamcommunity.com/login/home/?goto=%2Fdev%2Fapikey>.