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Project Gutenberg (often abbreviated PG) is a volunteer effort to digitize, archive, and distribute cultural works. Founded in 1971, it is the oldest digital library. Most of its items are the full texts of public domain books. The project tries to make the items in its collection as free as possible, in long-lasting, open formats that can be used on almost any computer.
Project Gutenberg was started by Michael Hart in 1971. Hart, a student at the University of Illinois, obtained access to a Xerox Sigma V mainframe computer in the university's Materials Research Lab. Through friendly operators, he received an account with a virtually unlimited amount of computer time; its value has since been variously estimated at $100,000 or $100,000,000. Hart has said he wanted to "give back" this gift by doing something that could be considered to be of great value.
This particular computer happened to be one of the 15 nodes on the computer network that would become the Internet. Hart believed that computers would one day be accessible to the general public and decided to make works of literature available in electronic form for free. He happened to have a copy of the United States Declaration of Independence in his backpack, and this became the first Project Gutenberg e-text.
By the mid-1990s, Hart was running Project Gutenberg from Illinois Benedictine College. More volunteers had joined the effort. Most text was entered manually until image scanners and optical character recognition software improved and became more widely available.
Hart later came to an arrangement with Carnegie Mellon University, which agreed to administer Project Gutenberg's finances. As the volume of e-texts increased, volunteers began to take over the project's day-to-day operations that Hart had run. In 1999 Walnut Creek CDROM released a two-CD set of the PG texts as of August 1999, titled Project Gutenberg: A Library containing over 1,600 Electronic Texts from the Project Gutenberg at Carnegie Mellon University.
In 2000, a non-profit corporation, the Project Gutenberg Literary Archive Foundation, Inc. was chartered in Mississippi to handle the project's legal needs. Donations to it are tax-deductible. Long-time Project Gutenberg volunteer Gregory Newby became the foundation's first CEO.
Also in 2000, Charles Franks founded Distributed Proofreaders, which allowed the proofreading of scanned texts to be distributed among many volunteers over the Internet. This effort greatly increased the number and variety of texts being added to Project Gutenberg, as well as making it easier for new volunteers to start contributing.
Pietro Di Miceli, an Italian volunteer, developed and administered the first Project Gutenberg website and started the development of the Project's online catalog. In his ten years in this role (1994–2004), the Project web pages won a number of awards, often being featured in "best of the Web" listings, and contributing to the Project popularity .
Starting in 2004, an improved online catalog made Project Gutenberg content easier to browse, access, and link to.
Scope of collection
In August 2006 Project Gutenberg claimed to have over 19,000 items in its collection, with an average of over fifty new eBooks being added each week. 
These are primarily works of literature from the Western cultural tradition. In addition to literature such as novels, poetry, short stories, and drama, Project Gutenberg also has cookbooks, reference works and issues of periodicals. The Project Gutenberg collection also has a few non-text items such as audio files and music notation files.
Most releases are in English, but there are also significant numbers in many other languages. In August 2006 the non-English languages most represented were (in order): French, German, Finnish, Dutch, and Spanish.
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Michael Hart said in 2004: "The mission of Project Gutenberg is simple: 'To encourage the creation and distribution of eBooks.'" 
A slogan of the project is: "break down the bars of ignorance and illiteracy", because its volunteers aim to continue spreading public literacy and appreciation for the literary heritage just as public libraries began to do in the early twentieth century.
Project Gutenberg is intentionally decentralized. For example, there is no selection policy dictating what texts to add. Instead, individual volunteers work on what they are interested in, or have available.
The Project Gutenberg collection is intended to preserve items for the long term, so they cannot be lost by any one localized accident. In an effort to ensure this, the entire collection is backed-up regularly and mirrored on servers in many different locations.
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Unlike some other digital library projects, Project Gutenberg does not claim new copyright on titles it publishes. Instead, it encourages their free reproduction and distribution.
Most books in the Project Gutenberg collection are distributed as public domain under U.S. copyright law. The legalese included with each eBook puts some restrictions on what can be done with the texts (such as distributing them in modified form, or for commercial purposes) as long as the Project Gutenberg trademark is used. If the header is stripped and the trademark not used, then the public domain texts can be reused without any restrictions.
There are also a few copyrighted texts that Project Gutenberg distributes with permission. These are subject to further restrictions as specified by the copyright holder.
In 1998 the Sonny Bono Copyright Term Extension Act extended the duration of already-existing copyright by twenty years. This has prevented Project Gutenberg from adding many titles that would otherwise have become public domain in the U.S.
Project Gutenberg has been criticized for lack of scholarly rigor in its e-texts: for example, in inadequate detailing of editions used and in the omission of original published prefaces and critical apparatus. A marked improvement in preserving such text can be seen by comparing earlier texts with newer ones; most new e-texts preserve edition information and prefaces.
All affiliated projects are independent organizations which share the same ideals, and have been given permission to use the Project Gutenberg trademark. They often have a particular national, or linguistic focus.
- Project Gutenberg Australia hosts many texts which are public domain according to Australian copyright law, but still under copyright (or of uncertain status) in the United States, with a focus on Australian writers and books about Australia.
- PG-EU is a sister project which operates under the copyright law of the European Union. One of its aims is to include as many languages as possible into Project Gutenberg. It operates in Unicode to ensure that all alphabets can be represented easily and correctly.
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Although Projekt Gutenberg-DE was given permission to use the Gutenberg name years ago, not everyone considers it to be an affiliated project, because of philosophical differences. Projekt Gutenberg-DE copyrights its product and limits access to browsable web-versions of its texts.
For a list of other similar projects, some of which have been inspired by Project Gutenberg, see the list of digital library projects.