Tutorial: How to become REUSE-compliant

This tutorial explains the basics of making a software project REUSE-compliant. The goal is to easily, comprehensively, and unambiguously declare your copyright and licensing in a way that is machine-readable. By the end of this tutorial, you will understand the three fundamental steps of REUSE:

1. Choose and provide licenses
2. Add copyright and license information to each file
3. Confirm REUSE compliance

For the purpose of this tutorial, we will assume that the directory of your project looks like this:

project/
├── src/
│   └── main.c
├── Makefile
└── README.md

If you would like to reproduce the steps in this tutorial on your own computer, you can clone the example repository. The branch non-compliant matches the structure above, while the compliant branch is the successful result of this tutorial.

For each of these steps, you will first learn how to achieve them manually. However, the REUSE tool supports you with most tasks, and the necessary commands will be listed as well in the collapsible boxes. We recommend to first understand the basic principle before just executing the tool’s commands.

1. Choose and provide licenses

The first thing you need to do is to choose a license. For this tutorial, we assume that you chose the GNU General Public License (GPL) v3.0 or any later version. More than simply choosing a license, you need to put the license in your project directory.

Find your license in the SPDX License List. SPDX is an open standard for communicating license and copyright information. Each license is uniquely identified by a shortform SPDX License Identifier. The SPDX License Identifier for your chosen license is GPL-3.0-or-later.

Create a LICENSES/ directory in your project root which will contain all the licenses that you use in your project. In your case, this means creating a file GPL-3.0-or-later.txt in this directory, which will contain the full license text. The name of the file is an SPDX License Identifier. You can find the license text for many Free Software licenses in the license-list-data repository.

2. Add copyright and licensing information to each file

Now that you have a license, you need to indicate in the relevant files that these files fall under that license. Edit the comment header of src/main.c as such:

/*
 * SPDX-FileCopyrightText: 2024 Jane Doe <[email protected]>
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

The SPDX-FileCopyrightText tag records the publication years and copyright holder of the contents of the file. You can read more about which publication years to use and what copyright holders are in the FAQ.

The SPDX-License-Identifier tag is followed by a valid SPDX License Expression, typically just the SPDX License Identifier of the license.

Each file must always contain these two tags in the header. You are allowed to use the SPDX-FileCopyrightText tag multiple times if you have multiple copyright holders.

In the example project, you also edit Makefile and README.md using this header information, but of course with corresponding comment syntax.

reuse annotate --copyright="Jane Doe <[email protected]>" --license="GPL-3.0-or-later" src/main.c Makefile README.md

3. Confirm REUSE compliance

Having added a license to your repository and having added copyright and licensing information to each file, your project tree will now look like this:

project/
├── LICENSES/
│   └── GPL-3.0-or-later.txt
├── src/
│   └── main.c
├── Makefile
└── README.md

To ensure that you did not miss anything, you should confirm REUSE compliance with the REUSE tool. Follow the installation instructions available for multiple platforms, then go to the project directory and run the linter.

$ reuse lint

# SUMMARY

* Bad licenses: 0
* Deprecated licenses: 0
* Licenses without file extension: 0
* Missing licenses: 0
* Unused licenses: 0
* Used licenses: GPL-3.0-or-later
* Read errors: 0
* Files with copyright information: 3 / 3
* Files with license information: 3 / 3

Congratulations! Your project is compliant with version 3.2 of the REUSE Specification :-)

As you can see in the last line, the tool confirms that your project is compliant with REUSE now! To learn what the different criteria mean, please have a look at the documentation of the lint command.

More information

This tutorial was a lightning-quick introduction to REUSE. Not all use-cases are covered here, especially how to annotate uncommentable files, how to bulk-annotate files, and how to use a license not on the SPDX list. In order to learn about these and more practical use-cases, see the ‘How do I …’ section in the Frequently Asked Questions.

Other sources for more information:

• Our Frequently Asked Questions covers common questions as well as extraordinary cases and will constantly be updated.
• The REUSE Specification may aid you in gaining a full understanding of REUSE.
• The REUSE tool documentation describes installation and usage of the REUSE tool.
• Our help for developers lists various resources for programmers like the tool, the API, or how to include checks in CI/CD workflows.

If none of the links above were able to answer your question, please contact us by:

• opening an issue on reuse-website for questions on the tutorial, FAQ or specification;
• opening an issue on reuse-tool for questions on the REUSE tool;
• or sending an email to the FSFE. Please note that we would prefer issues because they are publicly searchable for other people.

Thank you for your valuable contribution towards making software reusable!