GPLAboutDialog is an extension of AbstractAction which uses JOptionPane to display an "About" dialog with the GPL disclaimer and a button to display the GPL. The GPL is assumed to be in a local file called liscence.txt but if it is not found, GPLAboutDialog will ask the user if it can attempt to download the license from the FSF website. The dialog accpets both an Icon for the progam dialog and a seperate Icon for the GPL dialog (if not found, the JOptionPane default is used instead). A default GNU logo is included, and so is a copy of the GPL, naturally.
