Avoid Legal Pitfalls: How License Auditor CLI Keeps Your Project Safe

The Licenses Problem

In the JavaScript ecosystem, adding a package to your project is as easy as running npm i in your terminal. Package files are updated, the dependencies are installed, and we’re free to enjoy the bounty of the vast npm repository. Well, this might not always be the case—every package has its license, and a plethora of licenses place additional burdens on the developer. These might include requirements for attribution, open access to the source code, or even prohibitions on gaining financial benefits.

Each of these packages can also have several dependencies, which have their own licenses and dependencies, ad infinitum. If the issue of package licenses is considered from the start of the project or identified early enough, the liability can be minimized through reasonable selection and understanding of license requirements. In the case of legacy projects where no one considered this problem, the issue could be far larger.

This is why we developed a configurable tool focused on auditing project dependencies—License Auditor CLI, or LAC.

Package Managers

JavaScript projects use a variety of package managers, each with its own way of handling dependencies. To make LAC as universal as possible, we ensured it supports multiple package managers, including npm, yarn, and pnpm.

For npm, we leverage Arborist, a library designed to traverse and analyze dependency trees in a structured and efficient way. Arborist allows us to gather information on direct and transitive dependencies, ensuring we have a complete list of packages used within a project.

For yarn and pnpm, we take a different approach, utilizing their built-in commands to retrieve dependency data. Specifically, we use yarn list for Yarn projects and pnpm ls for pnpm-managed repositories. These commands provide structured outputs that allow us to extract relevant information about installed packages and their versions, ensuring that LAC can seamlessly analyze projects regardless of the package manager being used.

Many Places to Hide a License

Once we identify all installed packages, the next step is determining their respective licenses. This isn't always straightforward, as licenses can be declared in multiple places within a package. LAC takes a comprehensive approach by checking the following sources:

• package.json files – Most packages include a license field in their package.json, making it the first and easiest place to look.

• LICENSE files – Some packages provide a dedicated LICENSE file containing the full legal text of their license. We scan for this file and attempt to match its content to known licenses.

• README files – In cases where a package does not include an explicit license declaration, the README file might contain license-related information.

While checking for LICENSE and README files, we employ text similarity calculations to recognize license texts even if they do not match predefined formats exactly. This helps us correctly classify licenses that may be expressed differently or contain minor textual variations.

A Tool Must Fit the Craftsman

One of LAC’s core strengths is its high level of configurability. Every project has its own licensing requirements, and we wanted to ensure that our tool could accommodate a variety of needs. LAC provides the following configuration options:

• Whitelist and Blacklist – Developers can define a list of allowed and prohibited licenses. If a package's license appears on the whitelist, it is marked as compliant. If it appears on the blacklist, it is flagged as a potential issue.

• Overrides List – Certain packages might require special treatment due to ambiguous licensing information or exceptions in company policies. The overrides list allows users to manually specify how certain dependencies should be classified, preventing false positives or unnecessary alerts.

By offering this level of customization, LAC ensures that teams can audit their dependencies in a way that aligns with their internal policies and legal requirements.

To make License Auditor CLI as flexible as possible, we provide multiple output options. Users can choose to:

• View results directly in the terminal – A concise, easy-to-read summary is displayed, highlighting compliant, unknown, and blacklisted licenses.

• Save results to a JSON file – This option is particularly useful for CI/CD pipelines and automated auditing, as it allows for integration with other tools and reporting systems.

By supporting both interactive and automated workflows, LAC fits seamlessly into modern development environments.

Summary

As software projects grow in complexity, managing dependencies becomes an increasingly critical task. The risk of introducing legally problematic licenses into a project can be significant, particularly when working with large dependency trees. By using tools like License Auditor CLI, developers can take a proactive approach to license compliance, ensuring that their projects remain legally sound and free from unexpected obligations.

Through its comprehensive package analysis, flexible configuration options, and multiple output formats, LAC provides a robust solution to the challenge of dependency license auditing. Whether starting a new project or reviewing an existing codebase, staying mindful of software licenses is crucial—and with License Auditor CLI, it’s easier than ever.