Howdy Dwayne,
Good question. When the license expires nothing really happens except you stop getting updates. Your site will continue to function as it did before, and you can even redownload/reinstall the plugin. You just will not get access future plugin updates that are released including bug fixes, and you will no longer be able to open support tickets here.
We don’t like it when some company holds you hostage by forcing you to relicense their product for the rest of your life, so we don’t do that either. The only caveat is that if you continue updating WordPress and your other plugins while the license is expired, one or more of those may eventually drop compatibility for the old version of our calendar that you are running. At that time you might wish to renew your license to get the updated version of our plugins so everything works together.
Does that answer your question?
Cheers!
– Brook