If you download a Tableau Public dashboard, you'll get access to the datasets that where use to make it.
I believe it is the same for Tableau Desktop dashboards.
Which leads me to : are Tableau Desktop documents, stored on a Tableau Server, downloadable by anyone with access to that link ?
I would like to publish a Tableau Desktop dashboard on a Tableau Server so I can put it on a website yet I don't want the viewers to be able to download the dashboard. Knowing this will likely determine whether or not I buy Tableau Server.