LiDetector: License Incompatibility Detection for Open Source Software

How can we effectively detect and resolve license incompatibilities in open-source software to mitigate legal risks and ensure compliance?

We recently conducted an insightful interview with researchers Dr. Xu Sihan and Prof. Liu Yang. Our discussion centered around the complexities of managing licenses in OSS projects and how their innovative tool, LiDetector, is helping address these issues. This groundbreaking work has been published in ACM Transactions on Software Engineering and Methodology. Stay tuned for key insights and expert perspectives on improving OSS license management and compliance.

Scantist: Could you start by giving us an overview of what LiDetector is and what it aims to accomplish?

SIHAN XU: LiDetector is a tool designed to automatically detect license incompatibilities in open-source software (OSS). It analyzes the licenses attached to software components—whether they’re official licenses like MIT or custom ones created by developers—and identifies conflicts between them. These conflicts can arise when the obligations of one license, like source code disclosure, contradict the restrictions of another. LiDetector uses a combination of machine learning and natural language processing to dynamically interpret these licenses and spot issues that could lead to legal risks for developers.

Scantist: Could you briefly introduce what motivated you to develop LiDetector, and what key issues you aimed to address in license incompatibility detection for open-source software (OSS)?

SIHAN XU: The main motivation came from seeing how complicated it’s becoming to integrate open-source software due to all the different licenses out there. Many projects are using third-party code, and with so many licenses—both official and custom—it’s easy to run into conflicts. We wanted to create something that could automatically spot these issues, especially with custom licenses, which aren’t handled well by existing tools. The goal was to minimize the legal risks for developers by catching these conflicts early on.

Scantist: LiDetector employs a learning-based method and Probabilistic Context-Free Grammar (PCFG) for detecting license incompatibility. Could you explain why you chose these techniques and how they improve accuracy over previous methods?

SIHAN XU: We chose PCFG because it helps break down the structure of license texts, which are often written in complex legal language. This allows us to identify the key rights and obligations. By combining it with machine learning, we’re able to go beyond predefined licenses and adapt to custom ones, which are a huge pain point for developers. This approach really boosts accuracy compared to older tools. Instead of relying on static rules, we’re interpreting license terms dynamically, which makes the system far more flexible and effective.

Scantist: Your large-scale study showed that over 72% of the 1,846 GitHub projects analyzed had license incompatibility issues. What does this say about the nature of these conflicts, and how should developers handle them?

SIHAN XU: Yeah, it was pretty eye-opening. A lot of these conflicts come from well-known licenses like MIT and Apache clashing with custom ones. For instance, something as simple as one license requiring source code disclosure while another forbids it creates a legal mess. Developers often aren’t even aware of these conflicts until it’s too late. The best way to handle this is to start checking license compatibility early in the project. If they’re using third-party components, tools like LiDetector can help catch these conflicts before they escalate into bigger problems.

Scantist: In your paper, you compare LiDetector to existing tools like FOSS-LTE. Could you share the specific advantages LiDetector offers in terms of detection accuracy and false positive/negative rates?

SIHAN XU: LiDetector stands out mainly because it adapts to both official and custom licenses. Existing tools like FOSS-LTE are good but limited to predefined licenses, which doesn’t reflect how most developers work these days. We were able to achieve over 93% precision, and what’s really impressive is how much lower our false positive and negative rates are compared to other tools. That’s crucial when you’re dealing with legal compliance—you don’t want too many false alarms, but you also can’t miss important issues. LiDetector strikes a good balance.

Scantist: How do you see LiDetector being used by developers and legal teams in practice? Are there specific scenarios where you think it will be most helpful?

SIHAN XU: I see it being used most in big projects where multiple third-party components are integrated. For developers, it’s great because it can automate a lot of the legal checking process, saving them from having to manually sift through licenses. For legal teams, it helps ensure compliance early on, especially in industries where legal risks are high. The tool shines in projects where custom licenses are involved because it catches conflicts that would otherwise fly under the radar. It’s really about preventing those “uh-oh” moments down the road.

Scantist: What improvements or expansions do you foresee for LiDetector? Are there other challenges in OSS license management that you want to tackle?

SIHAN XU: There’s definitely room to grow. One thing we’re looking at is scalability—making sure LiDetector can handle even larger ecosystems of licenses. Another area is expanding beyond just license incompatibility. We’re interested in looking at patent rights and even linking license issues with security vulnerabilities. The machine learning model could also be refined to adapt faster to new licensing trends. Ultimately, we want to make this tool indispensable for developers working in complex environments where legal and security concerns overlap.

Scantist: Based on your research, what advice or best practices would you recommend for developers and organizations managing OSS licenses?

SIHAN XU: One of the big takeaways is that you’ve got to be proactive. A lot of developers don’t think about license compatibility until it’s too late. Integrating a tool like LiDetector into your development pipeline can save you a lot of headaches. Custom licenses, while they can be useful, introduce complexities that need to be carefully managed. Having a solid licensing strategy from the beginning and using the right tools to check for conflicts can make all the difference. It’s about being smart from the start.

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