GNU Affero General Public License v3 - An Overview

by Rowan Wilson on 22 April 2008 , last updated


The Affero General Public License v3 is an adapted version of the GNU General Public License v3, designed to better protect software whose chief use is providing useful services over a network. It can be read in full at .

History of the Affero GPL

Founded in 2001 in San Francisco, Affero is a company that provides a means for members of online communities to rate and reward other members for their work. As well as offering this service, Affero also makes the underlying software that implements the service available. Initially the licence for Affero’s software was an adapted version of the GNU GPL v2 that they created in-house. More recently they have moved to an adapted version of the GNU GPL v3, written in collaboration with its authors, the Free Software Foundation, called the Affero GPL v3.

Affero’s intention in adapting GPLs v2 and v3 is to ensure that licensees who make adaptations of their work will contribute the source code of these adaptations back to the community. As the provision of services over the web has become a bigger and bigger sector of the economy, some observers have become concerned that such service providers are reaping huge benefits from the use of free and open source software without returning anything to the community that created it. After all, such companies are not actually distributing their versions of the software in question, just exposing its functionality to users over networks like the web. As they are not distributing the software, they have no responsibility to make the source code to their version available. This has become known as the ‘ASP (Application Service Provider) loophole’. It should be noted that there is not equanimity across the free and open source community on whether this ‘loophole’ is in fact a problem in need of a formal solution. Communities based around permissively-licensed open source software tend to believe that adapted code is often made available even without legal compulsion to do so.

When the GPL v3 was being drafted , Affero and others argued that it should contain provisions that plugged this service provision ‘loophole’. In the end, though, the Free Software Foundation decided that they would instead help Affero create a new version of their licence based upon the GNU GPL v3 and allow software authors to choose which licence best suited their code and intentions. The Free Software Foundation now manages the licence itself, and has added ‘GNU’ to its name to reflect this. In March 2008 the Open Source Initiative approved the GNU Affero GPL v3, after it was submitted to them by open source mobile data-syncing firm Funambol.

Main Features of the Affero GPL v3

In order to close the ‘ASP loophole’, Affero had to engineer a situation in which source code could be obtained from a service provider independently of any act of distribution of the software. Thus the GNU Affero GPL v3 stipulates that any adaptation of software that it covers must prominently offer its source code for download to users who interact with it over a network. In addition to this condition, the AGPL v3 also explicitly permits software to be created by combining code which is under the GPL v3 and the AGPL v3. In this case the resulting software would be under a combination of both licences, with each section of code retaining its original licence. In all other respects the GNU Affero GPL v3 is identical to the GNU GPL v3.

What Does The Affero GPL v3 Do?

These bullets are intended to summarise what is distinct about the Affero GPL v3. They are not intended as a full description of its features. The Affero GPL v3:

  • closes the ‘ASP loophole’ by mandating the delivery of source code by service providers
  • ensures that modified versions of the code it covers remain free and open source

Open Source Development - An Introduction to Ownership and Licensing Issues explains the principles of open source licensing.

Further reading


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