Anytime you vary from common practices, everyone has to know what is going on. If the owner waived the corkage fees, whoever supplies the wine needs to know that well in advance.

This need not be unpleasant, simply letting the wine supplier know that there will only be one glass per person. If that is not satisfactory, you are the host and have a choice which is either calling the owner back and asking to have the fee reinstated or telling your friend that the one glass sticks.

No matter what, the tip ought to be calculated as though there had been a corkage fee if the staff did anything beyond clear the one glass.

These sorts of issues can be uncomfortable at the restaurant and are best dealt with out of sight beforehand.