Zend Framework is licensed under the Open Source Initiative (OSI)-approved New BSD License. for ZFv1 all code contributors must sign a Contributor License Agreement (CLA) based on the Apache Software Foundation’s CLA. The licensing and contribution policies were established to prevent intellectual property issues for commercial ZF users, according to Zend's Andi Gutmans.ZF2 is CLA free
Zend Framework (ZF) is an open source, object-oriented web application framework implemented in PHP 5 and licensed under the New BSD License
Zend Framework version 1.7 requires PHP 5.2.4 or later. Previous versions required PHP 5.1.4 or later, although the ZF Programmer's Reference Guide strongly recommended PHP 5.2.3 or later for security and performance improvements included in these versions of PHP. Zend Framework 2.0 requires PHP 5.3.3 or later. PHPUnit 3.0 or later is required to run the unit tests shipped with Zend Framework. Many components also require PHP extensions.