Pixelorama is a free and open-source 2D sprite editor, made with the Godot Engine, using GDScript!
Pixelorama uses Godot 3.2, so you will need to have it in order to run the project. As of right now, most of the code is written using GDScript, so the mono version of Godot is not required, but Pixelorama should also work with it.