The people responsible for EGS4...
The EGS4 software was developed by Richard Ford, a student of SLAC in the mid-1970's and (Walter) Ralph Nelson, a current employee in the Radiation Protection Group at SLAC, for everyday use at SLAC related to design of experiments.
Starting in the early 80's Dave Rogers of the National Research Council of Canada in Ottawa, Canada realized that EGS4 had enough content to be of enormous use for medical physics applications. At the same time, Hideo Hirayama of the KEK in Japan, was interested in the low-energy problem as well and so Nelson, Rogers and Hirayama want about making changes to EGS (then EGS3) resulting in the release of EGS4 in December 1985.
In 1982 Dave Rogers was joined by a recent graduate of Stanford University, Alex Bielajew, a mathematical theorist who was interested in making EGS4 much more reliable for medical-physics applications. The adaptations that resulted in the December 1985 release of EGS4 made it difficult for anyone who was a non-EGSpert to make the code give the correct answers. The result of this work was an adaptation of EGS4 called PRESTA for Parameter Reduced Electron-Step Transport Algorithm. Bielajew has been working on making the calculation of electron problems more accurate and reliable ever since. He also has been responsible for creating and distributing the UNIX and VAX versions of the code.
Hideo Hirayama was joined by Yoshihito Namito who introduced many important capabilities to the code, particularly in the low-energy photon modeling regime, such as polarization, corrections for atomic binding and Doppler broadening.
Other people have helped with various aspects of the code development and distribution. Suzan Walker of the Lanzl Institute of Medical Physics in Seattle created and distributes the PC version of the EGS4 code. The Lanzl Institute has also hosted two of the highly successful EGS4 courses, whereby researchers from around the world meet, usually in an attractive location, to learn about the innards of EGS4 and then get hands-on experience with an EGSpert looking over their shoulders.
Much of the work of distributing and publicizing the EGS4 code have come about from the effort of Rick Donahue and Rob Stewart who maintain the EGS4 Web site. The EGS4 Web site is a primary source of technical information about EGS.
No one can really claim ownership of EGS4 anymore, although it is copyrighted by Stanford University and the Government of Canada through the National Research Council. It is really the child of a thousand mothers and fathers. One of the best things about EGS4 is that it is free and its design is open so that others can make changes to it easily, after an initial learning period.
If you really want to learn more about the history of the EGS4 code, there is a document you can read. It also has some details about recent improvements to EGS4.