“There are a number of ways traditional software vendors can
participate in the open source software community. They circulate
around open source licenses, such as the GNU General Public License
(GPL), and how to leverage open source software as a marketing
tool.“A sophisticated marketing application of the GPL is the dual
license. The dual-license approach is not typically one integrated
license. It is a business policy that permits a customer to choose
one of two licenses: either a typical commercial license or an open
source license such as the GPL…”