From the Preface: “This is a translation of an old book—indeed, in Internet time, it is a translation of an ancient text.” That text is Lessig’s “Code and Other Laws of Cyberspace.” The second version of that book is “Code v2.” The aim of Code v2 is to update the earlier work, making its argument more relevant to the current internet.
Code v2 was written in part through a collaborative Wiki. That version is still accessible here. Lessig took the Wiki text as of 12/31/05, and then added his own edits. Code v2 is the result.
The Wiki text was licensed under a Creative Commons Attribution-ShareAlike 2.5 License. So too is the derivative. Reflecting the contributions of the community to this new work, all royalties have been dedicated to Creative Commons.
You can download the full text in PDF form. The text is also available in a Wiki hosted by SocialText. And obviously, you can also buy the book at the links to the right. (A wise choice, as it is cheaper than printing the book in most contexts.)