GIMP was originally released as the General Image Manipulation Program. In 1995 Spencer Kimball and Peter Mattis began developing GIMP as a semester-long project at the University of California, Berkeley for the eXperimental Computing Facility. In 1996 GIMP (0.54) was released as the first publicly available release. In the following year Richard Stallman visited UC Berkeley where Spencer Kimball and Peter Mattis asked if they could change General to GNU (the name given to the operating system created by Stallman). Richard Stallman approved and the definition of the acronym GIMP was changed to be the GNU Image Manipulation Program. This reflected its new existence as being developed as Free Software as a part of the GNU Project.
The number of computer architectures and operating systems supported has expanded significantly since its first release. The first release supported UNIX systems, such as Linux, SGI IRIX and HP-UX. Since the initial release, GIMP has been ported to many operating systems, including Microsoft Windows and macOS; the original port to the Windows 32-bit platform was started by Finnish programmer Tor M. Lillqvist (tml) in 1997 and was supported in the GIMP 1.1 release.
Following the first release, GIMP was quickly adopted and a community of contributors formed. The community began developing tutorials, artwork and shared better work-flows and techniques.
GIMP is primarily developed by volunteers as a free and open source software project associated with both the GNU and GNOME projects. Development takes place in a public git source code repository, on public mailing lists and in public chat channels on the GIMPNET IRC network.
New features are held in public separate source code branches and merged into the main (or development) branch when the GIMP team is sure they won't damage existing functions. Sometimes this means that features that appear complete do not get merged or take months or years before they become available in GIMP.
GIMP itself is released as source code. After a source code release installers and packages are made for different operating systems by parties who might not be in contact with the maintainers of GIMP.
The version number used in GIMP is expressed in a major-minor-micro format, with each number carrying a specific meaning: the first (major) number is incremented only for major developments (and is currently 2). The second (minor) number is incremented with each release of new features, with odd numbers reserved for in-progress development versions and even numbers assigned to stable releases; the third (micro) number is incremented before and after each release (resulting in even numbers for releases, and odd numbers for development snapshots) with any bug fixes subsequently applied and released for a stable version.
Each year GIMP applies for several positions in the Google Summer of Code (GSoC); to date GIMP has participated in all years except 2007. From 2006 to 2009 there have been nine GSoC projects that have been listed as successful, although not all successful projects have been merged into GIMP immediately. The healing brush and perspective clone tools and Ruby bindings were created as part of the 2006 GSoC and can be used in version 2.8.0 of GIMP, although there were three other projects that were completed and are later available in a stable version of GIMP; those projects being Vector Layers (end 2008 in 2.8 and master), and a JPEG 2000 plug-in (mid 2009 in 2.8 and master). Several of the GSoC projects were completed in 2008, but have been merged into a stable GIMP release later in 2009 to 2014 for Version 2.8.xx and 2.9.x. Some of them needed some more code work for the master tree.
If you have been to class regularly, we have walked you through all of the tools and some of the filters available in GIMP. If you need a reminder, you can go to this website for specific information on each tool.