At the Linux Kongress conference in 1998, Matthias Ettrich did a presentation to see how easily he could convert some existing code to use a technology called Qt (pronounced "cute"). Ettrich chose to use the graphic application GIMP as a base. The night before the conference, Ettrich wrote 1,100 lines of code that used this newer Qt technology. He took the GIMP code base and showed how it could be converted with little effort. This created disagreements in the GIMP community.
At the time, there was an existing KDE application called Kimage that was started by Matthias Elter. Another individual, Michael Koch, would later name the project KImageShop. Elter became busy with the KDE project, so KImageShop stopped being worked on for a time.
In 2000, John Califf became the new maintainer. His initial enthusiasm and passion for the project resurrected it and put the code base in a good state. In this time, KImageShop changed names again to Krayon. The passion and progress were only temporary, so Krayon lost steam. It was 2001. In the next year, Krayon was not touched.
In 2002, Patrick Julien took over the project. Before he could do much work, Krayon had to be renamed after legal disputes. The name Krita was finally decided upon. Julien continued to work on refactoring the code base. In 2003, Boudewjin Rempt came on board to help development. When Rempt started, Krita was once again in a state of disrepair. Most of the tools were not working at the time.
Since Rempt became the maintainer, the development has picked up considerably. Other developers began to join such as Sven Langkamp, Cyrille Berger, Casper Boemann, Adrian Page, and Michael Thaler.
In 2004, Krita had its first public release after 5 years of development. The press seemed to enjoy this new painting application as well. At this time, Krita was focused on being a generic image editing and painting application.
In 2009, the focus of the application shifted solely to painting. The community also began to establish a development fund to pay developers for their work. The project started participating in the Google Summer of Code program. The Blender Foundation also began using Krita for their preproduction work on Sintel.
In 2013, the Krita Foundation was formed. This foundation was made to provide support for development. The foundation has since used other platforms such as Kickstarter to provide funding.
References
Multi Toolkit Programming: Interoperability of different GUI toolkits for the X Window System
History
The History of KImageShop / Krayon / Krita