Software Licenses

The agreements that govern code

This section covers the most widely used open source licenses for software. Each license page explains the terms, typical use cases, and practical implications.

License Families

Licenses are grouped by their philosophical approach:

Permissive Licenses

These licenses grant maximum freedom with minimal requirements—typically just attribution.

• MIT

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  Simplest and shortest. The default for JavaScript, Ruby, and general-purpose projects.

• Apache 2.0

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  Includes patent grant. Standard in enterprise, Java, and Cloud Native ecosystems.

• BSD

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  Academic origins. Common in BSD systems and networking projects.

Copyleft Licenses

These licenses require derivative works to preserve the same freedoms.

• GPL

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  Strong copyleft. Applies to the entire combined work.

• LGPL

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  Weak copyleft. Only library modifications must be shared.

• MPL 2.0

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  Weak copyleft. Only modified files must be shared.

Other Licenses

Special cases that don't fit neatly into the above categories.

• Public Domain

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  No restrictions. Maximum freedom, no attribution required.

• AGPL

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  Network copyleft. Closes the "SaaS loophole" for web services.

• Source Available

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  Not open source. Code is viewable but usage is restricted.

Choosing a License

For guidance on selecting a license for your own project, see the Choosing a License guide.

License Identifiers

Each license has an SPDX identifier—a short, standardized code used in package managers and license scanners:

• MIT - MIT License
• Apache-2.0 - Apache License 2.0
• GPL-3.0-only - GNU General Public License v3.0 only
• GPL-3.0-or-later - GNU General Public License v3.0 or later

Using SPDX identifiers in your projects helps automated tools understand your licensing.