But Kelty became a hacker of culture, not software. At Rice University, where he was an assistant professor of anthropology until earlier this year, he participated in the Connexions project, working to create a community of people who write educational materials, share them freely, and build on and repackage each other's work. He also helped write licenses for Creative Commons, an organization that extends the practices of free software to visual art, music, and writing. Like free-software licenses, many Creative Commons licenses protect users' rights to modify and share creative work.

Two Bits "is a chance to articulate how the culture of free software is significant," Kelty says. "Not just the mechanics of how does it work, but what does it mean?" He says people could use his book to apply practices common to free software elsewhere.

The book is available free at Twobits.net, where readers are invited to transform it as they see fit.