So the asset includes sprite sheets which are just .png files. Those wouldn't require any special program. The other asset isn't necessary since this one also contains template sprites (the other pack is the only one with normal maps for the template though)
You'll also have a .JSON file which is the metadata for the sprite sheet according to the Aseprite format. It lists the animations, which frames they contain, and how long they last. Some game engines use this to import animations.
Aseprite is optional, but it includes everything used to create the sprite sheets with some scripts to mix and match costumes. There should be a README file that explains it.
The Godot & Unity sample projects just exist so people can see how the animations can be imported or are intended to look in practice, as it can be hard to visualize with the sprite sheet being so massive.
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