Thanks for pointing this out, and apologies for the glitch in our release process! We will update the link soon. In the meantime, if you need access to the docs, they are in the distribution zip that you have downloaded from https://mindmaps.io/pages/documentation/resources/downloads.html
Just to let you know that the API reference docs are now in place here https://mindmaps.io/pages/api-reference/latest/index.html for v 0.4.0. Earlier versions are linked from the API reference page.
Well done Jo!