See these links for the API's.
Also, if you want to build a portal using Tableau, this can kinda be done. We did this for some prototyping. See Piedmont's example as I think this is the most well known. Tableau Zen: Customizing the Tableau Server experience (Part 1)
This typically falls in the Tableau Server admin area which is why I moved it.
Please expand on Question 2 as it doesn't make sense. Tableau Desktop is only used for building reports. It cannot be used for portal or other web design.
The video requires Adobe Flash Player which is a security issue for some organizations. Also, while their portal looks nice it is of no value to the two questions at hand. Was there something else on the page that explained how to build a portal in Java that I missed?