SpeakOut! licenses are for use on a single site. In the Pro version (i.e. a license has been verified) there is a button to “revoke license key” which will revert the SpeakOut! plugin to the free version and make the key available to be used elsewhere.
Perhaps you have installed it on a development site and are ready to move to a production site, if so (or for any other reason), you can revoke the license key and then verify on your new site with the same key.