About Open Source Licenses

Choosing the right open source license is crucial for your project. It defines how others can use, modify, and distribute your code. This tool helps you understand the differences between popular licenses and generate the appropriate license text for your project.

Why License Your Project?

• Legal protection: Protect yourself from liability and warranty claims
• Clear permissions: Tell users what they can and cannot do with your code
• Encourage contribution: Contributors need to know the licensing terms
• Professional credibility: Licensed projects are taken more seriously
• Repository platforms: GitHub and others recommend adding a license

License Comparison

MIT License (Most Permissive)

Best for: Projects where you want maximum adoption and minimal restrictions

Used by: jQuery, Rails, Node.js, React, .NET Core

• Very short and simple to understand
• Allows commercial use without restrictions
• Only requires preserving copyright notice
• No requirement to share source code of derivative works
• Most popular license on GitHub

Choose MIT if: You want your code to be used as widely as possible without restrictions

Apache License 2.0 (Permissive with Patent Grant)

Best for: Projects where patent protection is important

Used by: Android, Apache projects, Swift, Kubernetes, TensorFlow

• Similar to MIT but longer and more explicit
• Includes explicit patent grant from contributors
• Requires documenting significant changes
• Better protection against patent litigation
• Preferred by corporations and large projects

Choose Apache if: You want permissive licensing with strong patent protection

GNU GPL 3.0 (Strong Copyleft)

Best for: Projects where you want all derivatives to remain open source

Used by: Linux kernel, WordPress, GIMP, Git, Bash

• Requires derivative works to use the same license
• Forces source code disclosure of modified versions
• Prevents incorporation into proprietary software
• Protects end-user freedom
• Includes patent grant and anti-tivoization provisions

Choose GPL if: You want to ensure all derivatives remain free and open source

BSD 3-Clause (Permissive with Attribution)

Best for: Projects that want MIT-like freedom with additional protections

Used by: Flask, Django, NumPy, PostgreSQL

• Very similar to MIT license
• Adds clause prohibiting use of author's name for endorsement
• Slightly longer but still simple
• Provides additional protection for project name/brand

Choose BSD-3 if: You want MIT-like freedom but don't want your name used for promotion

BSD 2-Clause (Simplified BSD)

Best for: Maximum simplicity with basic protections

Used by: FreeBSD, OpenBSD

• Even simpler than BSD-3-Clause
• Removes the "no endorsement" clause
• Essentially equivalent to MIT with different wording

Choose BSD-2 if: You want the simplest possible permissive license

GNU LGPL 3.0 (Weak Copyleft)

Best for: Libraries that can be used in proprietary software

Used by: Qt, GTK, FFmpeg, VLC

• Like GPL but allows linking with proprietary code
• Modified library code must remain open source
• Applications using the library can be proprietary
• Good compromise for libraries

Choose LGPL if: You're creating a library and want it usable in commercial software

Mozilla Public License 2.0 (File-level Copyleft)

Best for: Projects that want to be mixed with proprietary code

Used by: Firefox, Thunderbird, LibreOffice

• Copyleft applies only to modified MPL files
• Can be mixed with proprietary code in same project
• More flexible than GPL, stricter than MIT
• Good balance for corporate acceptance

Choose MPL if: You want copyleft but allow mixing with proprietary code

The Unlicense (Public Domain)

Best for: Dedicating work to the public domain

Used by: Small utilities, sample code, educational projects

• Gives up all rights to the work
• No conditions or limitations whatsoever
• Anyone can do anything with the code
• No attribution required

Choose Unlicense if: You want to give your code to the world with zero restrictions

Quick Decision Guide

• I want maximum adoption: MIT or BSD-2-Clause
• I want patent protection: Apache 2.0
• I want derivatives to stay open source: GPL-3.0
• I'm making a library for any use: MIT or Apache 2.0
• I'm making a library that should stay open: LGPL-3.0
• I want per-file copyleft: MPL-2.0
• I want no restrictions at all: Unlicense

Common Misconceptions

• Myth: "No license means it's free to use"
  Reality: Without a license, all rights are reserved by default. Others cannot legally use your code.
• Myth: "MIT means no credit required"
  Reality: MIT requires including the license and copyright notice in derivatives.
• Myth: "GPL means you can't sell software"
  Reality: You can sell GPL software, but buyers can redistribute it freely.
• Myth: "Apache and MIT are identical"
  Reality: Apache includes explicit patent grants and requires documenting changes.

How to Add a License

1. Generate the license: Use this tool to create your license text
2. Create LICENSE file: Save the license as "LICENSE" (no extension) in your project root
3. Add copyright notices: Include copyright headers in source files if required
4. Update README: Mention the license in your README.md
5. Package metadata: Include license in package.json, setup.py, etc.
6. Commit and push: Add LICENSE to version control

License Headers in Source Files

Some licenses require or recommend adding headers to source files:

// Copyright (C) 2024 Your Name
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0

Multiple Licenses (Dual Licensing)

Some projects offer multiple license options:

• Example: "Licensed under MIT OR Apache-2.0"
• Benefit: Users can choose which license to follow
• Common in: Rust ecosystem (MIT OR Apache-2.0)

Important Notes

• Not legal advice: This tool provides information, not legal advice. Consult a lawyer for specific situations.
• Read the full license: Understand all terms before choosing
• Check dependencies: Ensure your license is compatible with your dependencies' licenses
• Can't revoke: Once code is released under a license, you can't revoke that version's license
• Can change future releases: You can change the license for new versions

Related Tools

• Gitignore Generator - Create .gitignore files
• License Header Inserter - Add license headers to source files
• Changelog Generator - Generate release notes
• Case Converter - Format license text
• Documentation Outline Generator - Create documentation structure

Further Reading

• Choose a License - GitHub's license guide
• OSI Approved Licenses - Open Source Initiative
• TLDRLegal - Plain English license summaries
• GNU License List - License compatibility