sandwicense

Sandwicense is a term coined to describe a licensing model that combines elements of both permissive and copyleft licenses. The term is a portmanteau of "sandwich" and "license," reflecting the way it layers permissive and copyleft provisions together. This hybrid approach aims to provide users with the flexibility of permissive licenses while also incorporating some of the protective measures found in copyleft licenses.

In a sandwicense, the core codebase is typically licensed under a permissive license, such as the MIT License or the Apache License 2.0. This allows users to freely use, modify, and distribute the code without significant restrictions. However, certain components or modules within the same project may be licensed under a copyleft license, such as the GNU General Public License (GPL) or the Affero General Public License (AGPL). These copyleft components are "sandwiched" between the permissive parts of the project.

The primary purpose of a sandwicense is to protect the copyleft components from being incorporated into proprietary software. By licensing these components under a copyleft license, the project maintainers ensure that any modifications made to these parts must be shared with the community, preventing them from being used to create closed-source software. This dual-licensing approach strikes a balance between encouraging collaboration and innovation (through permissive licensing) and safeguarding the integrity of the project's open-source nature (through copyleft licensing).

Sandwicenses are particularly useful in projects where certain components have specific legal or ethical requirements that necessitate copyleft protection. They allow project maintainers to offer a more flexible licensing environment while still addressing the concerns that necessitate copyleft provisions. Examples of sandwicenses include the Mozilla Public License (MPL) 2.0, which is often used in conjunction with permissive licenses like the MIT License.