Understanding Open-Source Licenses: A Guide for Developers

Choosing the right license for your open-source project is crucial—it defines how others can use, modify, and distribute your code. With so many options available, it can be overwhelming to decide which one fits best. In this post, we’ll break down the most popular open-source licenses, their key differences, and when to use them.

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1. MIT License – The Permissive Choice

✅ Best for: Projects that want maximum adoption with minimal restrictions.

The MIT License is one of the most popular permissive licenses. It allows users to:

• Use, copy, modify, merge, publish, distribute, sublicense, and sell the software

• Include the original copyright notice and license in all copies

🔹 Why use it?

• Simple and short

• Encourages widespread use (used by React, Ruby on Rails, and many Node.js projects)

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2. GNU General Public License (GPL) – The Copyleft License

✅ Best for: Projects that want all derivatives to remain open-source.

The GPL (v2/v3) ensures that any modified or distributed versions of the software must also be open-source under the same license.

🔹 Key Features:

• Allows modification and distribution

• Requires derivative works to be GPL-licensed

• Ensures software freedom

🔹 Why use it?

• Protects against proprietary forks (used by Linux, WordPress)

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3. Apache License 2.0 – Permissive with Patent Protection

✅ Best for: Projects that want permissive terms with explicit patent rights.

The Apache 2.0 License is similar to MIT but includes:

• A grant of patent rights from contributors

• Protection against patent litigation

🔹 Why use it?

• Used by Kubernetes, Android, and Apache projects

• Good for corporate-backed open-source projects

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4. BSD Licenses (2-Clause & 3-Clause) – Minimalist and Business-Friendly

✅ Best for: Projects that want minimal restrictions and avoid endorsement issues.

• BSD 2-Clause: Allows free use but requires copyright notice

• BSD 3-Clause: Adds a "no endorsement" clause

🔹 Why use it?

• Used by FreeBSD, Redis, and early versions of macOS

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5. GNU Affero GPL (AGPL) – Strong Copyleft for SaaS

✅ Best for: Projects that want to prevent SaaS companies from using code without sharing changes.

The AGPL extends the GPL by requiring source code disclosure even for network services.

🔹 Why use it?

• Used by MongoDB (before switching to SSPL)

• Ensures cloud providers contribute back

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6. The Unlicense – Public Domain Dedication

✅ Best for: Developers who want to waive all rights.

The Unlicense effectively places your work in the public domain, allowing unrestricted use.

🔹 Why use it?

• Maximum freedom (used by SQLite)

• Rarely used in corporate projects due to legal ambiguity

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Which License Should You Choose?

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Final Thoughts

• Want maximum adoption? → MIT or Apache

• Want to enforce open-source derivatives? → GPL/AGPL

• Working with patents? → Apache 2.0

• Avoiding legal complexity? → BSD