Doubts about named user license in CMC.

Hi Gurus,

I'm kinda new to this issue, our client has a named license for only eight users, while testing we realized that a user can logon several times with the same user name in different computers. My questions are, What would be the potential costs that this may entail?, why can I logon several times with the same user?, Is there a way to logon on a computer ending the same user logged on another computer? I have read different posts but I can't find answers to these questions.

thanks in advance.