A 'free-trial' that requires a Credit Card number is not a 'free-trial'. Do some extra programming to ensure that the free-trial stops working on the target co

A 'free-trial' that requires a Credit Card number is not a 'free-trial'. Do some extra programming to ensure that the free-trial stops working on the target computer after a set time or number of uses*, and throws up a notification that the 'free-trial' has been used for X number of times or for X number of days and won't be available any more. Your clients are then free to choose whether to buy your full system or try out some other system. This model is similar to what some News websites do. IIRC, "The New York Times". * I believe a set number of uses is more useful than a set number of days. Some clients won't use the app every day, and at the end of a month (say), may only have used the app twice and so haven't got a worthwhile feeling of its value.