See the project page on Github for more information.
As of Feb 2020, this project is up-to-date with Gen 8 (Pokémon Sword/Shield and its DLC). All old images from Gen 7 (Pokémon Ultra Sun/Ultra Moon) are still available for legacy support.
Archived versions of the legacy overview pages:
The sprite images are © Nintendo/Creatures Inc./GAME FREAK Inc.
Everything else, and the programming code, is governed by the MIT license.