To open the project, you will need version 3.6.2 of Godot, which you can download here: https://godotengine.org/download/archive/3.6.2-stable/
For the backgrounds, you can use this tool to make them: https://mrpedrobraga.itch.io/modot-distortionator The version of the addon in that link is newer than the version used in this project, so you will need download the Godot Integration Addon 1.0.5 and install it into the project's addons folder.
BEFORE YOU RUN THE GAME, make sure to enable the Distortionator Integration plugin in the Project Settings and RELAUNCH Godot.
Encore uses an Aseprite script called EncoreJsonExporter used for character animations. If you want to make new animations, please use this instead of bashing your head against the YAML wall.