Please refer to the Tableau EULA as the definitive answer to your licensing questions: Tableau License
With this in mind... here are answers to your questions:
Modifying the dashboard and workbook capability will require a license for Tableau server (TS)? YES.
...interactor will provide the capability to modify and publish the workbook on TS or it just to view and interact the existing workbooks? This is also a TS licensed user.
Also review the site rules for users for additional information on how user roles change the capabilities of the users.
Hope this was helpful.
Hi Siva ,
The eco-system you are talking about has majorly 2 applications provided by tableau
1. Tableau desktop - from where a person can develop reports and share it with other by publishing it ,It installed on local machine
2. Tableau server - It is a place where tableau desktop developer publish reports those were developed on Tableau desktop .It installed on windows server machine (most cases )
Now in terms of licenses at high level both products has their own licensing theory . every developer must have his own tableau desktop license so if you are planning for N developers you need to buy N tableau desktop licenses . They come with one time cost and then Maintenance charges every year .
For Tableau server there are Core based and User based licenses available . Simple Core based license allow any number of users to access tableau server however you will have restriction on using Cores (CPU's ) and for User based Licenses you will have freedom to add any number of cores to your architecture but you will have restriction on number of users . Again They come with one time cost and then Maintenance charges every year .
Link mentioned by Brian is good source for learning site roles and licensing .
Its recommended to discuss all these licensing things with account managers (tableau assign a person to each account who manages things like that ) .Some times for promoting business you may get good deal .