How SCA Tools Detect and Analyze Licenses

Modern SCA tools employ multiple techniques to identify licenses accurately. Simple detection matches declared licenses in package metadata against known license identifiers. However, metadata often contains errors, ambiguities, or missing information. Advanced tools scan actual source files for license headers, README files, and LICENSE documents. Natural language processing identifies license text even when modified or combined with other licenses.

License expression parsing handles complex scenarios where components use multiple licenses. SPDX expressions like "MIT OR Apache-2.0" indicate dual licensing where users choose applicable terms. "MIT AND CC-BY-4.0" requires compliance with both licenses. Some components use different licenses for different files or purposes—documentation under Creative Commons, code under Apache. SCA tools must parse these expressions correctly to determine actual obligations.

Transitive license analysis traces license obligations through dependency trees. A MIT-licensed direct dependency might include GPL-licensed transitive dependencies, creating unexpected obligations. Effective tools map these relationships, identifying where restrictive licenses enter dependency chains. They distinguish between different usage types—development, testing, runtime, or distribution—as obligations vary. This comprehensive analysis reveals the true license landscape of modern applications.