Developers of the programming language PHP are planning to update the PHP interpreter and Zend Engine engine licenses to a 3-button BSD license. This transition will simplify licensing terms, unify licenses for PHP and Zend Engine, ensure compatibility with GPL, and solve long-standing issues while preserving user and developer rights. The new license is expected to be implemented in the PHP 9.0 release, possibly next year. All members of the PHP Group have approved the license change, and the proposal is currently open for general discussion.
The current PHP license is approved by the Open Source Initiative (OSI) but is deemed incompatible with GPL due to the requirement of written permission for using the word “PHP” in derivative works. This has drawn criticism from Debian developers.
Initially, PHP 1.X and 2.X branches were released under the GPLv2 license. The PHP 3 branch introduced the PHP License along with GPL. Subsequently, PHP 4 shifted to distributing the main code under the PHP License and placing the Zend Engine engine, the primary PHP interpreter, in a separate “Zend/” subdirectoryzend Engine license. The Zend Engine License, like the PHP License, includes usage restrictions on the word “ZEND” in derivatives and mandates acknowledgement of engine usage in promotional materials.