Implementation:Apache Druid Licenses Registry

Knowledge Sources	Apache_Druid
Domains	Licensing, Compliance, Infrastructure
Last Updated	2026-02-10 10:00 GMT

Overview

licenses.yaml is a structured registry of all third-party dependency licenses bundled with or adapted into the Apache Druid project, required for Apache Software Foundation compliance.

Description

This YAML file contains multi-document entries (separated by ---) that declare every third-party library, source adaptation, and binary dependency used by Druid. Each entry records the dependency name, version, license category (source or binary), the Druid module it belongs to, the license name, optional copyright and notice text, and the specific library coordinates or source paths affected. The file spans over 6800 lines and covers hundreds of dependencies across categories including Apache-licensed libraries, MIT-licensed components, BSD-licensed code, and Eclipse-licensed JARs.

Usage

Reference this file when adding a new third-party dependency to Druid, when auditing license compliance, or when generating the NOTICE and LICENSE files for a Druid release distribution. The Apache release process requires all bundled dependencies to be declared here.

Code Reference

Source Location

• Repository: Apache Druid
• File: licenses.yaml
• Lines: 1-6820

Signature

# Each YAML document follows this structure:
---
name: <dependency or adapted code name>
license_category: source | binary
module: <druid module path>
license_name: <SPDX or descriptive license name>
version: <version string>           # optional
copyright: <copyright holder>       # optional
license_file_path: <path to license file>  # optional
libraries:                           # for binary dependencies
  - <groupId>: <artifactId>
source_paths:                        # for source adaptations
  - <path within repo>
notice: |                            # optional NOTICE text
  <notice content>

Import

# Parse the license registry (example with Python)
python -c "
import yaml
with open('licenses.yaml') as f:
    for doc in yaml.safe_load_all(f):
        if doc:
            print(doc.get('name'), '-', doc.get('license_name'))
"

I/O Contract

Inputs

Name	Type	Required	Description
name	string	Yes	Human-readable name of the dependency or adapted source code
license_category	string	Yes	Either "source" (code adapted into Druid) or "binary" (JAR/library bundled at runtime)
module	string	Yes	The Druid module or extension that uses this dependency
license_name	string	Yes	Name of the license (e.g., "Apache License version 2.0", "MIT License")
version	string	No	Version of the third-party dependency
libraries	list	No	Maven coordinates (groupId: artifactId) for binary dependencies
source_paths	list	No	Repository paths for adapted source code
notice	string	No	NOTICE text required by the dependency license

Outputs

Name	Type	Description
LICENSE file	text	Generated LICENSE file content for Druid distributions
NOTICE file	text	Generated NOTICE file content aggregating all notice texts

Usage Examples

Adding a New Binary Dependency

---
name: Example Library
license_category: binary
module: java-core
license_name: Apache License version 2.0
version: 1.2.3
libraries:
  - com.example: example-lib

Declaring Adapted Source Code

---
name: algorithm adapted from Example Project
license_category: source
module: processing
license_name: MIT License
copyright: Example Author (https://github.com/example/project)
license_file_path: licenses/src/example.MIT
source_paths:
  - processing/src/main/java/org/apache/druid/example/AdaptedAlgorithm.java