The SkookumScript plugin is published on the Unreal Engine Marketplace. If you are a new user, it is recommended that you install it via the Epic Games Launcher.
Latest Build (zip file)
It can sometimes take a while for Epic Games to make the latest update to the SkookumScript UE4 Plugin available on the Unreal Marketplace. If you are a power user or are impatiently waiting for an update, you can download a precompiled version of the plugin directly from the GitHub Releases page.