I don't understand. Why couldn't a post-install script copy the file from a previous installation if it existed? If the key is expired, you are no worse off than you were to start, as your old copy was expired, too, and you were going to have to manually update it anyway.
Maybe even a step added to the GUI (say as part of dbtest?) that would allow you to clikc and have the file moved? Better yet, follow the standard method of saving the new config file as filename.rpmnew and keeping the old one. That would require a new location for the file, but...
Maybe you could store the license in the DB?
It's really annoying to have to move the license with each upgrade. I have never seen another piece of software where this is needed.
Tom