Short for Lesser General Public License, the license that accompanies some open source software that details how the software and its accompany source code can be freely copied, distributed and modified. A Lesser General Public License is used to license free software so that it can be incorporated into both free software and proprietary software, and is often referred to as the weaker sibling of GPL. The LGPL and GPL licenses differ with one major exception; with LGPL the the requirement that you open up the source code to your own extensions to the software is removed. The most widespread use of LGPL is in reference to the GNU LGPL. LGPL is also called GNU libraries and formally called the Library GPL.