license glib
GLib is a bundle of five low - level system libraries written in C and developed mainly by GNOME . GLib code was separated from GTK + , so it can be used by software other than GNOME and has been developed in parallel ever since . The ___MASK49___ ( LGPL ) is a free software license published by the Free Software Foundation ( FSF ). The license allows developers and companies to use and integrate software released under the LGPL into their own ( even proprietary ) software without being required by the terms of a strong copyleft license to release the source code of their own components . The license only requires software under the LGPL be modifiable by end users via source code availability . For proprietary software , code under the LGPL is usually used in the form of a shared library such as a DLL , so that there is a clear separation between the proprietary and LGPL components . The LGPL is primarily used for software libraries , although it is also used by some stand - alone applications . The license was originally called the GNU Library General Public License and was first published in 1991 , and adopted the version number 2 for parity with GPL version 2 . The LGPL was revised in minor ways in the 2 . 1 point release , published in 1999 , when it was renamed the ___MASK49___ to reflect the FSF ' s position that not all libraries should use it . Version 3 of the LGPL was published in 2007 as a list of additional permissions applied to GPL version 3 . GTK + ( formerly GIMP Toolkit ) is a cross - platform widget toolkit for creating graphical user interfaces . It is licensed under the terms of the ___MASK49___ , allowing both free and proprietary software to use it . It is one of the most popular toolkits for the Wayland and X11 windowing systems , along with Qt .