UOAssist is licensed much like UO, that is per account. So you'll need
to buy a license for each account you wish to use UOAssist with in the
game.

To get UOAssist to produce the extra seeds:
1) Login to the game with the extra account.
2) Go to the UOAssist registration dialog.
3) Notice the seed value. If you are logged in with a different account
the value should have changed to match the current account.

To setup UOAssist to use multiple keys.
1) Go to the registration dialog in UOAssist.
2) Click on the button 'Key:' (right before the key field).
A dialog box will come up that allows you to enter up to 8 keys.
UOAssist will scan each key upon login to see if any of them are valid
for the current game session.