It looks like it's mostly self-contained and it doesn't seem to have a clear way to leverage Godot, which is a pity. It uses it's own script language, own resources, etc. It'd be really interesting to have something like this, and have full access to Godot, use shaders, custom nodes, plugins like LimboAI, Beehave, etc.

By looking at the screenshots I thought this looks a lot like Godot. So there is my answer ;)