*GPL:* Copyleft licenses - ensure that the software or derivates always stay Free too. ~(Linux)~ *BSD-Style:* License that basically allows you to do everything with the software, even making it closed source, although usually some restrictions apply. ~(Apache and PHP)~ *GPL and proprietary:* Dual-licensed because GPL might be "too" free. ~(MySQL, eZ publish)~ *FLOSS Exception:* Exception to the GPL so that Free Software can use MySQL's client libraries. ~(MySQL client library)~