The firmware-only USB driver for AVR microcontrollers is published under the terms of the GNU General Public License Version 2 (GPL). See the file "License.txt" in the "usbdrv" subdirectory of any reference project for details. In addition to the terms and conditions of the GPL, we strongly recommend that you also do the following:
If the terms and conditions of the GPL are unsuitable for you, e.g. because you don’t want to publish the source code of your firmware, you can simply pay money for a commercial V-USB license. As an additional benefit you get USB PIDs for free, dedicated exclusively to you. For detailed terms and conditions please download the latest version of V-USB and check the file "CommercialLicense.txt". We offer the following licenses:
Primarily for people who originally intended to use the free license, but find it too tedious to prepare the publication, or people who need a dedicated USB Product ID. This license allows you to build up to 5 units of your design for non-commercial purposes. It comes with one VID/PID pair licensed exclusively to you.
For up to 150 units, including one VID/PID pair licensed exclusively to you.
A virtually unlimited license (fair use), including two VID/PID pairs licensed exclusively to you. You may use this license to produce any number of units, as long as you don’t get into the Big Business (less than about 10,000 units).