From Introduction:
Ecosystems collapse - deadly new viruses plague humanity - offworld colonies provide a refuge to the wealthy - megacorporations handle the real power in the world - the Internet virtual reality extends across the globe and the colonies - man fuses with machine, using cybernetic implants and genetic modifications to become superhuman and achieve immortality.
This is cyberpunk, science fiction at its best and darkest. Pioneered by writers like William Gibson and Philip Dick and by cult movies like Blade Runner, the cyberpunk genre is about a dark future - a future not as far away as we would like to believe.
The CYD20 project is a giant sourcebook intending to bridge the cyberpunk genre with the d20 system, effectively allowing you to stage cyberpunk campaigns using your favorite game system. It attempts to deal with all different aspects of cyberpunk: characters, equipment, hacking and computers, cyberware and bioware, etc. No game world details are provided in CYD20: the book is a collection of rules and mechanics to be used in your own campaigns.