The Common Public Attribution License ("CPAL") is a free software license

Free software licence

A free software licence is a software licence which grants recipients rights to modify and redistribute the software, which would otherwise be prohibited by copyright law. A free software licence grants, to the recipients, freedoms in the form of permissions to modify or distribute copyrighted work...

 approved by the Open Source Initiative

Open Source Initiative

The Open Source Initiative is an organization dedicated to promoting open source software.The organization was founded in February 1998, by Bruce Perens and Eric S. Raymond, prompted by Netscape Communications Corporation publishing the source code for its flagship Netscape Communicator product...

 in 2007. Its purpose is to be a general license for software distributed over a network. It is based on the Mozilla Public License

Mozilla Public License

The Mozilla Public License is a free and open source software license. Version 1.0 was developed by Mitchell Baker when she worked as a lawyer at Netscape Communications Corporation and version 1.1 at the Mozilla Foundation...

, but it adds a controversial attribution term paraphrased below:
The CPAL also adds the following section discussing "network use" which triggers copyleft

Copyleft

Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work...

 provisions when running CPAL licensed code on a network service and this way closing the so called ASP loophole:

External links

• CPAL version 1.0 text at the Open Source Initiative
• Free Software Foundation opinion on compatibility with GPL.