Licensing Considerations

Any time you link libraries together or distribute software, you need to be concerned with the licenses of the underlying code. Some software licenses - like the GPL - can require that any code linked with them be subject to the license and therefore be made open source. In addition, many licenses require a license and/or copyright notice be attached to works that use or are derived from the project using that license. So when building or distributing any software, you need to be cognizant about all the software going into the final work and any licensing terms that apply. Binaries produced with PyOxidizer are no different!

PyOxidizer and the code it uses in produced binaries is licensed under the Mozilla Public License version 2.0. The licensing terms are generally pretty favorable. (If the requirements are too strong, the code that ships with binaries could potentially use a weaker license. Get in touch with the project author.)

The Rust code PyOxidizer produces relies on a handful of 3rd party Rust crates. These crates have various licenses. We recommend using the cargo-license, cargo-tree, and cargo-lichking tools to examine the Rust crate dependency tree and their respective licenses. The cargo-lichking tool can even assemble licenses of Rust dependencies automatically so you can more easily distribute those texts with your application!

As cool as these Rust tools are, they don’t include licenses for the Python distribution, the libraries its extensions link against, nor any 3rd party Python packages you may have packaged.

Python and its various dependencies are governed by a handful of licenses. These licenses have various requirements and restrictions.

At the very minimum, the binary produced with PyOxidizer will have a Python distribution which is governed by a license. You will almost certainly need to distribute a copy of this license with your application.

Various C-based extension modules part of Python’s standard library link against other C libraries. For self-contained Python binaries, these libraries will be statically linked if they are present. That can trigger stronger license protections. For example, if all extension modules are present, the produced binary may contain a copy of the GPL 3.0 licensed readline and gdbm libraries, thus triggering strong copyleft protections in the GPL license.


It is critical to audit which Python extensions and packages are being packaged because of licensing requirements of various extensions.

Consider using a package such as pip-licenses to generate a license report for your Python packages.

Showing Python Distribution Licenses

The special Python distributions that PyOxidizer consumes can annotate licenses of software within.

The pyoxidizer python-distribution-licenses command can display the licenses for the Python distribution and libraries it may link against. This command can be used to evaluate which extensions meet licensing requirements and what licensing requirements apply if a given extension or library is used.