ProcessWire is a pure open-source CMS licensed under the Mozilla Public License 2.0. When indicated in the file header, the MIT license is also used by ProcessWire.
For your own original code/files, you are not required to maintain the same license. Third party modules, your own templates, and your own site profiles may use different licenses at your discretion, so long as they are not incompatible with those used by ProcessWire. Third party libraries used by ProcessWire specify their own compatible license in file headers or in a LICENSE.* or README.* file present in the same directory. Files native to ProcessWire that do not indicate license in file header or in the directory can be assumed to be MPL 2.0 (Mozilla Public License v2.0).
MPL 2.0 LicenseMost files in the ProcessWire core source code use the Mozilla Public License, version 2.0.
MIT LicenseSome specific components in ProcessWire core use the MIT license (where specified).
3rd party filesThird party files may in ProcessWire may specify their own license. This page contains more details.
CLAProcessWire Contributor License Agreement (CLA), based on the language from the GitHub CLA.