Myriador were responsible for the conversion of some of the Fighting Fantasy gamebooks to the d20 System.
From the Myriador website:
Who Are We?
A group of experienced Role-Play fanatics based in England who thought it would be cool to earn a living through the hobby we love.
What Are We Doing?
Our aim was to produce Role-play material that we want to use. We aimed to produce modules and games that are of the highest quality, at the most reasonable prices, with as many useful extras as possible, to make the DM and players' experience as fun and hassle free as possible.