What is a Dual License Anyway?
Make it easier for users and remove the word “Dual” from your software project notice vocabulary.
“This project is licensed under a Dual License of BSD and GPL.”
What does “Dual” mean in this context? In a practical sense, it means you have to dig more deeply into the licensing for that project to figure out what this license statement means:
- Both the BSD AND GPL apply? (conjunctive)
- Or choose between BSD OR GPL? (disjunctive)
- Which version of BSD?
- And which version of GPL?
Typically, but not always, this example statement means that you have a choice of BSD-3-Clause OR GPL 2.0 or later because these are the most common versions of those licenses. As the consumer of the software project you must conclude that interpretation and choice, usually after exploring the other license notices in the project files. You must declare that choice in the attribution of your project(s) or product(s) that use that software.