Licensing

WP-CLI is licensed under the MIT license. This document outlines WP-CLI's licensing expectations for third-party code.
Accepting third-party code into the official repository/organization
All code accepted into repositories under the official WP-CLI GitHub organization must be compatible with the MIT license. This ensures that WP-CLI can remain freely usable, modifiable, and distributable by anyone.
Bundling third-party code
When bundling third-party code directly into a WP-CLI package (i.e., copying code into the repository rather than declaring it as a dependency), the code must:
Be licensed under an MIT-compatible license
Include the original license file or header - The third-party code's license terms must be preserved
Maintain copyright notices - Original copyright notices must remain intact
Be clearly identified - It should be clear which code is third-party and where it came from
When in doubt about whether to bundle third-party code, consider using it as a dependency through Composer instead.
Depending on third-party code
Third-party packages declared as dependencies (through Composer or other package managers) must be licensed under MIT-compatible licenses. This applies to both:
Direct dependencies - Packages explicitly listed in 
composer.json
Transitive dependencies - Dependencies of your dependencies
Checking dependency licenses
Before adding a new dependency:
Check the dependency's 
LICENSE file or 
composer.json for license information
Verify that all of the dependency's own dependencies are also compatible
Use 
composer show -t to view the dependency tree with license information, or install additional tools like 
composer/satis to run 
composer licenses for detailed license auditing
Why these requirements?
These licensing requirements ensure that:
WP-CLI remains free and open - Users can use, modify, and distribute WP-CLI without legal concerns
Commercial use is permitted - Companies can use and integrate WP-CLI into their products
No license conflicts - All code in the WP-CLI ecosystem is legally compatible
Simplicity for users - Users don't need to track multiple license requirements
Questions?
If you have questions about licensing or need clarification on whether a specific license is compatible, please open an issue or contact the WP-CLI maintainers.