A little background around Tableau. Tableau is not free although there are versions free to use (there is a difference) and there is a free use period, after which you must pay for the software.
Tableau offers five main products:
Tableau Desktop
Tableau Server
Tableau Online
Tableau Reader
Tableau Public
Tableau Public and Tableau Reader are free to use, while both Tableau Server and Tableau Desktop come with a 14-day fully functional free trial period.
Tableau is also not considered to be open source (as R and D3 are, for example), but Tableau is designed to support how you think, utilizing drag and drop to create visualizations of your data and leverage your natural ability to spot visual patterns quickly.
The foundation of Tableau combines a Structured Query Language (SQL) for databases with a descriptive language for rendering graphics, to invent a database visualization language called Visual Query Language (VizQL), making Tableau a unique tool for creating data visualizations...