I am not as succinct as Faterson, but I will give a bit more explanation...
You can 'register' anywhere you like. Because this is a FLASH game, it's not played on your computer but directly from WGT's servers. Since, however, each computer can only run one Flash at a time, you would not be able to play 2 accounts on one computer at the same time.
Now, a word of warning, if you have two accounts that play from one computer, and one of you starts to get really good, there may be talk of 'multiple accounts'. I would make sure that each of you plays your own account. Perhaps a short note to members@worldgolftour.com to explain your situation would be in order before there are any questions.
but then again, that's just my 2¢...