Here are copies of the binaries distributed from https://www.duckstation.org/libretro/ and used in Batocera.
The libretro core is provided under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives International License (BY-NC-ND 4.0). COMMERCIAL DISTRIBUTION AND USAGE IS PROHIBITED. By downloading the libretro core, you agree that you will not distribute or utilize it with any paid applications, services, or products. This includes server side use in streaming environments. Put simply, it is free for personal use, but you are not allowed to utilize DuckStation to make money.
The core is maintained by a third party, and is not provided as part of the Duckstation GitHub release. Its changelog is viewable here.