I like this add-on but it wants permission to do just about anything. I don't see how displaying a flag requires:
accessing my data for all websites
exchanging messages with programs other than Firefox
inputting data to the clipboard
downloading files and reading and modifying the browser's download history
displaying notifications to me
accessing browser activity during navigation

The only reasonable permission to grant an add-on for displaying a flag is:
access browser tabs

Until/unless this changes I refuse to use this add-on. Displaying a flag may be nice, but is nowhere near being essential. The license may be free, but that doesn't make the requested permissions any less ridiculous.