Caudium is the name of a GPL-ed (free for commercial and personal use) web server written in Pike and in C. It is originally based on the Roxen Challenger 1.3 code base.
It is an attractive alternative to servers like Apache, Netscape® and Zeus® due to its strength in dynamic page and data generation, modularity and more.
The Caudium Project runs also an IRC network, has created a GPL webmail called CAMAS and has an ever-growing community of developers and users worldwide.