GIMP is primarily developed by volunteers as a free software project associated to 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.