Open Source Software License Management

When using free / open source software (FOSS) libraries it is important to understand their terms and conditions. The same holds true when publishing your own software using a FOSS license.

There are a great many different open source software licenses. I recommend to use one of the licenses that is approved by either Free Software Foundation (FSF) or Open Source Initiative (OSI).

The Software Package Data Exchange (SPDX) provides an excellent overview in their SPDX License List. The site provides each of the licenses' full name, identifier, full text and whether or not they are approved by any of the above organisations.

Publish Your Own Code as FOSS

When publishing your own code as FOSS, you need to decide which license to use. For this purpose, start by consulting choose an open source license.

After chosing an appropriate license, add it to your project by commiting a LICENSE.txt file. You should also add it to your project's package description file if applicable (eg. package.json for node projects or Python's

Ideally, also add a license headers in each source file stating the copyright holder(s), year and the license's short name. You may even want to mention the license in the project's

Tools for Managing Licenses of Open Source Dependencies

License Finder

License Finder detects the licenses of the packages your software depends. It works with package managers (like pip or npm) to find your dependencies. When integrated in your CI process, it can ensure upon every push that all dependencies have licenses that are accepted by your policies.

For this to work, your policy has to be defined in configurable list of permitted licenses. For example, your .dependency_decisions.yml could include

- - :permit
  - Apache-2.0
  - :who: Gerald Senarclens de Grancy
    :why: Permissive OSI approved license w/out conflicts for us
    :versions: []
    :when: 2021-10-01 18:07:00.097448338 Z
- - :permit
  - MIT
  - :who: Gerald Senarclens de Grancy
    :why: Permissive OSI approved license w/out conflicts for us
    :versions: []
    :when: 2021-10-01 18:14:08.047430689 Z

To install license_finder, type

sudo gem install license_finder

If you prefer to install license_finder in your home directory, type

gem install --user-install license_finder


After installing all of your dependencies, launch license_finder with

license_finder --python-version=3 --decisions-file=.dependency_decisions.yml

license_finder can easily be included in the free tier of Gitlab's CI/CD pipelines (.gitlab-ci.yml) as well as GitHub's actions (.github/workflows).


Another great tool is FOSSology. It is an open source license compliance software system and toolkit. It can run license, copyright and export control scans from the command line. In contrast to License Finder, it also offers a complete compliance workflow based upon a database and web UI.

The workflow allows to generate an SPDX file, or a README with the copyrights notices from your software.

Proprietary Solutions

There are many proprietary solutions that offer scanning for open source license compliance. They usually also include scanning for security vulnerabilities, but come with a considerable price tag. The first prominent one was Black Duck, however meanwhile there are many alternatives. One of them is the most expensive tier of GitLab.