MCO isn't ready yet.
You'r propably talking about "Mars Colony - Demo" and not "Mars Colony Online".
MCO test server is on-line usualy on weekends.
New test = new (better!) game version needed to download.
That's why keep an eye out on this board: http://hyperkat.com/litterbox/index.php?board=8.0
Post Hyper your desired name and password if you wish to test with us. Otherwise, you won't be able to join in.
Basicly - you play the game with us, and if you find some bug's/glitches, you post them onto forum so that they may be repaired.
If you just play the demo, you propably won't find many peeple to join you at random. You would be better to find them on-line first. If yo have STEAM, you can join and play with Mars Colony fanclub.
At any rate: MCO is better than the Demo. It's bigger, more complex, more ppl can play, it has new equipement, outposts, dangers etc..
Ther's even an Easter Egg there....the oryginal Mars-base from Demo near the left edge of the map :-)