Date as program limitation
You should check a current date with date, which is limit to executing of your application. Check this condition in your *.dpr file.
uses SysUtils, Dialogs; ... begin if Date<EncodeDate(2003,3,9) then begin Application.Initialize; Application.CreateForm(TForm1, Form1); Application.Run; end else ShowMessage('The available period of this application has already finished'); end.