Amazon’s Kindle Direct Publishing has updated its publishing rules and  banned the distribution of public domain content that is available to anyone. Here is more from the update:

Some types of content, such as public domain content, may be free to use by anyone, or may be licensed for use by more than one party. We will not accept content that is freely available on the web unless you are the copyright owner of that content. For example, if you received your book content from a source that allows you and others to re-distribute it, and the content is freely available on the web, we will not accept it for sale on the Kindle store. We do accept public domain content, however we may choose to not sell a public domain book if its content is undifferentiated or barely differentiated from one or more other books.

Author Seth Godin shared the update on his blog, where he commented: “With a wide-open, long tail platform, this is going to be very tough to enforce, but they’re right–having someone selling 10,000 books each computer generated and each based on Wikipedia content wasn’t good for anyone.” (Via PaidContent.org).