>> "But how do we tell TFS not to try and access the LimeLM servers in normal use?"
The TFS will try to re-verify with the servers every X + Y days regardless of whether the customer offline activated or not: https://wyday.com/limelm/help/turbofloat-server/#config-isgenuine
The difference between offline and online activation is how it handles the failure to reverify with the servers after X + Y days.