LicenseRef- and AdditionRef- Prefixes

Not all license texts are present on the SPDX License List. The SPDX legal team uses the SPDX License Inclusion Principles to evaluate whether particular license and exception texts are appropriate to add to the List.

To represent a license that is not on the License List, you can create a custom identifier using a LicenseRef- prefix.

For example:

# SPDX-License-Identifier: LicenseRef-MyLicense

indicates that the content is subject to a license whose text is not on the SPDX License List.

# SPDX-License-Identifier: MIT WITH AdditionRef-MyExtraRequirement

indicates that the content is subject to the MIT license, with additional text that is not on the SPDX License List.

More details on the formatting for LicenseRef- and AdditionRef- syntax can be found in the SPDX License Expression Syntax.

Of course, because the license text or addition text is not on the SPDX License List, you will likely still need to communicate to the recipient which specific text corresponds to the custom identifier. Practices such as the FSFE REUSE Software specification can be helpful in defining standard locations to include license text in your repository.