Is Claude Code open source?

No. Claude Code is proprietary software owned by Anthropic. Its public GitHub repository, anthropics/claude-code, has a LICENSE.md that reads "© Anthropic PBC. All rights reserved," and says use is subject to Anthropic's Commercial Terms of Service. A public repository is not the same as an open source licence. Some related Anthropic projects are MIT licensed.

What does "open source" actually require?

Open source is a licence condition, not a visibility setting. The Open Source Initiative's Open Source Definition opens with: "Open source doesn't just mean access to the source code." A licence qualifies only if it meets ten criteria, among them:

1. Free redistribution. Anyone may give away or sell the software as part of a larger distribution, without a royalty.
2. Source code. The program must include source code and allow distribution in source and compiled form.
3. Derived works. The licence "must allow modifications and derived works," and allow them to be shared under the same terms.
4. No discrimination against fields of endeavour. It may not forbid use in, for example, a business.

A repository you can browse on GitHub meets none of these by itself. What matters is the licence file and any terms it points to.

What licence does Claude Code use?

The LICENSE.md in the repository, read on 16 October 2026, is one line: "© Anthropic PBC. All rights reserved. Use is subject to Anthropic's Commercial Terms of Service." "All rights reserved" means the copyright holder grants no general permission to copy, modify or redistribute, which fails criteria 1 and 3 above.

The npm package says the same thing in its metadata. The registry entry for @anthropic-ai/claude-code, version 2.1.301 when we read it, gives its licence as "SEE LICENSE IN README.md". The package is small (seven files, 189,328 bytes unpacked) and pulls in a separate platform package for each system, such as @anthropic-ai/claude-code-linux-x64 and @anthropic-ai/claude-code-darwin-arm64, as optional dependencies. The README now marks the npm install as deprecated and recommends the native installers instead.

What the repository does offer in public is documentation, an issue tracker ("file a GitHub issue") and a set of plugins that "extend functionality with custom commands and agents". You can read and report; the licence does not let you fork and ship your own version.

Which Anthropic projects around it are open source?

Several companion projects carry real open source licences. Read each one carefully, because a permissive repository licence can still sit next to service terms.

Project	Licence shown	Notes, read 16 October 2026
Claude Code (anthropics/claude-code)	All rights reserved	Use subject to the Commercial Terms of Service
Claude Agent SDK for Python (anthropics/claude-agent-sdk-python)	MIT, per the repository	README: use "is governed by Anthropic's Commercial Terms of Service"; the package bundles the Claude Code CLI
Claude Code GitHub Action (anthropics/claude-code-action)	MIT	Standard MIT text, "Copyright (c) 2025 Anthropic, PBC"
Codex CLI (openai/codex), for comparison	Apache-2.0	Per the CodeLifter agents ledger, 15 October 2026

The Agent SDK repository shows the trap clearly. GitHub labels it "MIT license", yet its README ends with a "License and terms" section saying use of the SDK is governed by the Commercial Terms of Service, "except to the extent a specific component or dependency is covered by a different license". And because the SDK installs a copy of the Claude Code CLI, the part that does the agent work is still the proprietary program. The MIT text in the Action repository is the plain permissive licence, with no extra terms in the file.

Does it matter for your project?

It matters in three situations.

• You want to change the tool. You cannot fork Claude Code and distribute a modified build. You can extend it with settings, skills, hooks, MCP servers and plugins, which is the route Anthropic documents.
• Your employer or school only allows open source tools. Claude Code does not qualify. The agents that do, such as the Codex CLI, are covered in the coding agents thread, and the CodeLifter agents directory lists the licence of twelve agents with its source.
• You care where your code goes. A licence does not answer that. Anthropic's costs page notes that "each Claude Code turn carries file contents, tool calls, and multi-step reasoning" to the model. The README also says Anthropic collects feedback, "which includes usage data (such as code acceptance or rejections), associated conversation data, and user feedback submitted via the /bug command." An open source client pointed at a hosted model sends your code out too; only a local model keeps it at home, as the local model thread explains.

The licence of the tool is also separate from the licence of the code it writes for you. That question is covered in the MIT licence thread.

How do you check any tool's licence yourself?

1. Open the LICENSE, LICENSE.md or COPYING file at the root of its repository and read it, not just the label GitHub shows.
2. Check the package registry. For npm, run npm view <package> license; "SEE LICENSE IN" means the real terms are elsewhere.
3. Read the README's licence or terms section. As the Agent SDK shows, it can add service terms on top of the file.
4. Check whether the package downloads another component, such as a bundled binary, and look up that component's licence too.
5. Compare what you find against the OSI list of approved licences. If the licence is not on it, treat the tool as proprietary.

The CodeLifter snippet licensing guide applies the same checks to code you copy.

Short version

• Claude Code is proprietary: its LICENSE.md says "All rights reserved" and points to Anthropic's Commercial Terms of Service.
• A public GitHub repository with an issue tracker and plugins does not make it open source.
• The Claude Code GitHub Action is MIT; the Python Agent SDK repository is MIT but its README adds the Commercial Terms, and it bundles the proprietary CLI.
• Read the licence file, the package metadata and the README before you call any tool open source.