You have to both have LS accounts already...then you go to:
http://www.project1999.org/forums/forumdisplay.php?f=25
Which is the "petition" forum on this site and there are instructions there for you to submit for an IP exemption.
Be careful with it...they do monitor and if you are caught 2-boxing (meaning you decide to play your roomates account while he isn't around etc... together at the same time as your own) they will ban the accounts.