The PHP License is designed to encourage widespread adoption of the source code.

Redistribution is permitted in source or binary form with or without modifications, with some caveats.

[4][5][3] The license is GPL-incompatible due to restrictions on the usage of the term PHP.

[3] Debian maintainers have had a long-standing discussion (since at least 2005) about the validity of the PHP license.

[9] Expressed concerns include that the license "contains statements about the software it covers that are specific to distributing PHP itself", which, for other software than PHP itself therefore would be "false statements".