A license is a contractual agreement between Wordfast LLC and the user to use the WFS software within certain limitations. A license is materialized as a code issued by the licensing party—usually Wordfast LLC—in response to a given Install number. The Install number of a WFS installation is found in the Setup > General pane. That number, as well as WFS’ version number, have to be provided to the licensing party (a sales agent at Wordfast LLC in most cases), who will in return provide a license number.
Note that the Install number is valid for a particular hard disk. If the hard disk is formatted (which can happen if Windows is re-installed), or if the hard disk is changed, the install number changes and a new license number must be obtained at no cost within the duration of the license agreement.