DuckStation is available as a libretro core, which can be loaded into a frontend such as RetroArch. It supports most features of the full frontend, within the constraints and limitations of being a libretro core.
The DuckStation libretro core is not covered by the GPL license, but is still completely free to use. The only restriction is that COMMERCIAL DISTRIBUTION IS PROHIBITED. By downloading the libretro core, you agree that you will not distribute it with any paid applications, services, or products.
The core is maintained by a third party, and is not provided as part of the GitHub release. The changelog is viewable at https://www.duckstation.org/libretro/changelog.txt
Builds can be downloaded from: