Why PHP 9.0 Is Switching to the 3‑Clause BSD License

License change for PHP 9.0

On 4 April 2024 the php.internals vote approved the RFC proposed by Ben Ramsey to release PHP 9.0 under the 3‑clause BSD (Modified/New BSD) license, replacing the dual licensing scheme of PHP License v3.01 for the runtime, extensions and interpreter framework and Zend Engine License v2.0 for the Zend/ directory.

Existing licensing situation

PHP License v3.01 is OSI‑approved; Zend Engine License v2.0 is not.

The PHP License contains a “no‑recognition” clause, a name‑restriction clause ("derived works may not be called ‘PHP’ …"), and a vague “reasonable use” clause.

These clauses were added to prevent a “PHP++" fork but require downstream packagers to perform license‑compatibility analysis for a license that is rarely used.

Why the 3‑clause BSD was chosen

It is a permissive OSI‑approved license that allows use, modification and redistribution.

It requires attribution in source and binary distributions.

It includes a trademark‑restriction clause that mirrors the intent of PHP’s original name‑restriction clause without the “no‑recognition” language.

Compared with the older 4‑clause BSD (which had an advertising clause) and the 2‑clause BSD (which drops the trademark restriction), the 3‑clause version provides a concise, permissive, attribution‑friendly compromise.

PostgreSQL license side note

PostgreSQL uses a custom “PostgreSQL License”, derived from BSD terms, without advertising, name‑restriction or endorsement clauses. Functionally it is equivalent to a dual‑clause BSD/MIT license, although OSI has not formally recognized it. The article notes that PHP could have retained a custom license and fixed its defects, but adopting a standard BSD‑style license removes the legal pain point for packagers with a single vote and commit.

Broader relevance

From 2024 to 2026 several projects (Redis, HashiCorp, Elastic, MongoDB) have moved from OSI‑approved licenses to custom “source‑available” licenses. PHP’s shift illustrates that standard permissive licenses remain attractive for both maintainers and downstream distributors. Projects still using bespoke licenses are encouraged to map their terms to an equivalent standard license before 2026.