License Guidelines

We only accept formulae that use a Debian Free Software Guidelines license or are released into the public domain following DFSG Guidelines on Public Domain software.

Specifying a License

All licenses are identified by their license identifier from the SPDX License List.

Specify a license by passing it to the license method:

license "MIT"

The public domain can be indicated using a symbol:

license :public_domain

If the license for a formula cannot be represented using an SPDX expression:

license :cannot_represent

Complex SPDX License Expressions

Some formulae have multiple licenses that need to be combined in different ways. In these cases, a more complex license expression can be used. These expressions are based on the SPDX License Expression Guidelines.

Add a + to indicate that the user can choose a later version of the same license:

license "EPL-1.0+"

GNU licenses (GPL, LGPL, AGPL and GFDL) require either the -only or the -or-later suffix to indicate whether a later version of the license is allowed:

license "LGPL-2.1-only"
license "GPL-1.0-or-later"

Use :any_of to indicate that the user can choose which license applies:

license any_of: ["MIT", "0BSD"]

Use :all_of to indicate that the user must comply with multiple licenses:

license all_of: ["MIT", "0BSD"]

Use :with to indicate a license exception:

license "MIT" => { with: "LLVM-exception" }

These expressions can be nested as needed:

license any_of: [
  "MIT",
  :public_domain,
  all_of: ["0BSD", "Zlib", "Artistic-1.0+"],
  "Apache-2.0" => { with: "LLVM-exception" },
]

Specifying Forbidden Licenses

The HOMEBREW_FORBIDDEN_LICENSES environment variable can be set to forbid installation of formulae that require or have dependencies that require certain licenses.

The HOMEBREW_FORBIDDEN_LICENSES should be set to a space separated list of licenses. Use public_domain to forbid installation of formulae with a :public_domain license.

For example, the following forbids installation of MIT, Artistic-1.0 and :public_domain licenses:

export HOMEBREW_FORBIDDEN_LICENSES="MIT Artistic-1.0 public_domain"

In this example Homebrew would refuse to install any formula that specifies the MIT license. Homebrew would also forbid installation of any formula that declares a dependency on a formula that specifies MIT, even if the original formula has an allowed license.

Homebrew interprets complex license expressions and determines whether the licenses allow installation. To continue the above example, Homebrew would not allow installation of a formula with the following license declarations:

license any_of: ["MIT", "Artistic-1.0"]
license all_of: ["MIT", "0BSD"]

Homebrew would allow formulae with the following declaration to be installed:

license any_of: ["MIT", "0BSD"]

HOMEBREW_FORBIDDEN_LICENSES can also forbid future versions of specific licenses. For example, to forbid Artistic-1.0, Artistic-2.0 and any future Artistic licenses, use:

export HOMEBREW_FORBIDDEN_LICENSES="Artistic-1.0+"

For GNU licenses (such as GPL, LGPL, AGPL and GFDL), use -only or -or-later. For example, the following would forbid GPL-2.0, LGPL-2.1 and LGPL-3.0 formulae from being installed, but would allow GPL-3.0

export HOMEBREW_FORBIDDEN_LICENSES="GPL-2.0-only LGPL-2.1-or-later"
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