I would offer a suggestion:
do not have it turn on during the first install.
have the user become familiar with the basic program and then when they come to need it, let them turn it on, let the trial period start when the need arises.
as a note, you my friend, have grabbed a tiger by the tail when you put this out for the world.
it is easy to find fault and to criticize, but just the fact that people are using it to find what they want to complain about means you are doing good, there is a need for this and that you are making a difference. I truly hope that this reaches the point of everyday use for throngs of us who need this sort of software. so, THANK YOU for your efforts.