What you need to do is make a Lite Version of your software and distribute it as shareware. Have an API initialization routine that must run for anything to work in the Lite Version. When the initialization is run, have a pop-up that says unregistered version, "can not be sold commercially." You are not reputable yet, and noone will pay for something from you. You have to have a package that people can download the Lite version, that includes sample code from examples and the examples. Professional companies do this.