You can read all about it here on the Koha wiki. It’s not something just for developers, we simply need people who are willing to put in some time documenting/testing/signing off on patches. Koha is and always has been a collaborative project with input from as many people as possible and since it’s release in 2000 has never been the domain of one company, or one set of people. The software grows in the direction the users want it to, come along, add your 2 cents and contribute to a Free Software project. You will be making the world a better place.