Affero General Public License

The Affero General Public License (Affero GPL and informally Affero License) refers to two distinct, though historically related, free software licenses. The first is the Affero General Public License, version 1 which was published by Affero, Inc. in March 2002, and is based on the GNU General Public License, version 2 (GPLv2). The second is compatible with the GNU Affero General Public License (a variant of the original Affero GPL license).

Both versions of the Affero GPL were designed to close a perceived application service provider (ASP) loophole in the ordinary GPL, where, by using but not distributing the software, the copyleft provisions are not triggered. Each version differs from the version of the GNU GPL on which it is based in having an added provision addressing use of software over a computer network. This provision requires that the full source code be made available to any network user of the AGPL-licensed work, typically a web application.

In 2000, while developing an e-learning and e-service business model, Henry Poole met with Richard Stallman in Amsterdam where they discussed the ASP loophole in GPLv2. Over the following months, Stallman and Poole discussed approaches to solving the problem. In 2001, Poole founded Affero Inc. (a web services business), and he needed a license that would require distribution by other organizations who used Affero code to create derivative web services. At that time, Poole contacted Bradley M. Kuhn and Eben Moglen of the Free Software Foundation to get advice on a new license that would close the ASP loophole in GPLv2.

Around late February 2002, Kuhn suggested, based on the idea of a quine (a program that prints its own source code), that GPLv2 be supplemented with a section 2(d) that would require derivative works to maintain a "download source" feature that would provide complete and corresponding source code. Kuhn argued that there was precedent for such a requirement in GPLv2 section 2(c), which required preserving certain features by downstream distributors and modifiers.

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