I am having the same problem. Is there a solution? The web version also seems to be broken.
Viewing post in Learn Godot's GDScript From Zero comments
You can build a working .dmg from source by importing the source code (can be found here: https://github.com/GDQuest/learn-gdscript) into Godot (you need to use Godot 3.x for this), and then exporting for OSX. Make sure you have the right export templates installed (you can do this automatically from Editor > Manage Export Templates...). Feel free to let me know if you get stuck! Or I can send you the .dmg