GCU (at the present time) is freeware for non-commercial use. You may use the fully-functional application for as long as you like, without restriction, but without support.

However, if you like GCU, find it useful, or use it in a commercial environment, please register your copy, knowing that you've contributed to the development of this application.

Registration costs just $29, and can be done with registration/credit card authorization handled by Paypal, a third-party company which provides secure on-line payment. The registration details are sent to me, and I will not divulge them to any third parties ...