That is a different question, once you create a char that then is limited to that server AFAIK in SWTOR.
But like most other MMO's if you want to change server with that char then you will probably can, but have to pay a premium to do that. I don't know whether SWTOR have that set up yet, but they will no to far down the line.
You can log onto another server and create a new char though.. hope that helps