This guide provides an overview of common open source licensing options, ranging from most restrictive (No License) to least restrictive (The Unlicense).

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No License (None)

  • By default, all creative works (including software) are automatically protected by copyright law. Without explicitly choosing a license, others cannot legally use, modify, or distribute your code. This default protection may be more restrictive than intended - choosing an open source license (described below) allows others to use your code while maintaining your copyright. More Information

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The Unlicense (Unlicense)

  • The most permissive option, dedicating your work to the public domain. Users can do anything with the code without any conditions - including using it in closed-source projects without attribution. More Information

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Permissive Licenses

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MIT License (MIT)

  • A popular, simple license requiring only that users preserve copyright and license notices. Allows commercial use, modification, and distribution under any terms. More Information

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Apache License 2.0 (Apache-2.0)

  • A permissive license whose main conditions require preservation of copyright and license notices. Contributors provide an express grant of patent rights. Licensed works, modifications, and larger works may be distributed under different terms and without source code. More Information

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BSD 2-Clause “Simplified” License (BSD-2-Clause)

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BSD 3-Clause “New” or “Revised” License (BSD-3-Clause)

  • Adds restriction on using contributors’ names for promotion without permission. More Information

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Copyleft Licenses

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GNU General Public License v2.0 (GNU GPLv2)

  • Strong copyleft requiring derivative works to use same license and provide source code. More Information

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GNU General Public License v3.0 (GNU GPLv3)

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GNU Lesser General Public License v2.1 (GNU LGPLv2.1)

  • Modified GPL for libraries, allowing linking without imposing GPL requirements. More Information

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GNU Lesser General Public License v3.0 (GNU LGPLv3)

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GNU Affero General Public License v3.0 (GNU AGPLv3)

  • Strongest copyleft, extends requirements to network-accessed software. More Information

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Mozilla Public License 2.0 (MPL-2.0)

  • A “weak” copyleft license requiring source code sharing for modified files only. Larger projects can use different licenses for new files. More Information

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Open Software License 3.0 (OSL-3.0)

  • A copyleft license with patent rights protection and special termination clauses for patent litigation. Doesn’t require reciprocal licensing for linked works. More Information

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Commercial Licenses

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Business Source License 1.1 (BSL 1.1)

  • A hybrid license allowing free use in many scenarios but requiring a commercial license for production use in business environments. Designed to balance open source principles with business sustainability. More Information