Today I discovered that the publisher O'Reilly, which produces a number of technology books, has honored the original U.S. copyright term by releasing many of its books 14 years and older under a CC Attribution license. Among these works is PNG: The Definitive Guide, available at the link in HTML format.

Uninteresting to the bulk of readers here, to be sure, but I thought the few graphics programmers among us might find it to be useful.