Four Leaf Studios (or 4LS, for short) is the group that developed and released Katawa Shoujo. After a doujin released in 2000 by Raita Honjou came to light, Four Leaf Studios began work on the visual novel based on a bonus page at the end of the one-shot.
Four Leaf Studios was made by frequenters of 4chan's /a/ board. Since discovering the bonus page (circa 2007), the members put a lot of time and effort into making the game into what it is today, finally releasing the finished product in January 2012.
Four Leaf Studios offers the full game and the demo (which was translated to several other languages) of Katawa Shoujo, as well as the soundtrack and other media for download at http://www.katawa-shoujo.com/. It is licensed under Creative Commons BY-NC-ND License , thus being free of charge.
Anonymous22 – Writer of Shizune's story. A22 also wrote about a third of Act 1.
Aura – Writer of Rin's story. Aura also wrote around a third of Act 1. The rest of act 1 was split more or less evenly between the other writers. Aura served as the "head writer", which meant that he wrote the scenario for Act 1 and handed whatever problems came up between writers, often serving as the last word.
cpl_crud – Original writer of Hanako's story. He was also the founded of 4LS, and was the producer from 2007 to 2010-11ish. According to Aura “Being a producer in 4LS means that you're kind of like a totem pole. The responsibilities are sparse, vague, mostly ceremonial and quite uncomfortable, but everyone depends on your existence on a weird emotional level even if you just stand there.”
Suriko – Writer of Lilly's story and parts of Hanako's route. Suriko also served as Producer after crud.
TheHivemind – Writer of Emi's story.
Kagami - editor
Silentcook - Head editor. SC did a vast majority of editing work.
It wasn't uncommon for images to have been worked on by 3-4 artists in the game
gebyy-terar - Side character design and art (Nurse, Mutou and Kenji)
Kamifish - Rin and Misha character artist
moekki - Shizune character artist and Emi sprite artist
Pimmy - Emi CG artist
weee - Hanako character artist
Raide - Lilly character artist
Additional Art climatic - Rin's in-story paintings and various cut-in illustrations
Doomfest - the background image for the classroom CG in Act 1 (it was done with 3D modeling, which none of the staff artists was that great with so they recruited "outside consultation")
yujovi - Yujovi took many of the source photographs for the game backgrounds.
cpl_crud – also took several pictures that were used for the game backgrounds.
delta - visuals direction, sound direction, music direction, special effects, user interface design, opening and ending movie
Raide - music direction
yujovi - music direction
delta - general engineering coding, scripting, release engineering, development infrastructure, media
and “Too many minor and former contributors to list”