Datahub isn’t launched public.
A license is tight to sales contracts.
via the link you find an overview of datahub and at the bottom you will have the option get in contact with Mendix about a license: https://www.mendix.com/data-hub/
It looks like Mendix Data Hub is now available. The documentation is avaliable as of Oct 5
It was released oct 1 afaik, but only accessible if you acquire a separate license for data hub. I think you need to contact Mendix sales to get access.