As Lessig says, there's a difference between free as in free speech, and free as in free beer. Today, the book is free as in free beer. But the day, and the causes to which the book proceeds go, both go go to free as in free speech.
Re Copyright: The book is copyright protected for 14 years, the term of copyright during the Founding generation. It disclaims copyright for the rest of the author's life plus the 70 years after death.
Plus all the proceeds, when people pay, for 14 years, goes to organizations fighting for Internet freedom.
It's not an expensive book, so people might want to1 donate to those causes directly, and more than $4.99.