SQL Server + Reporting Services + SSIS + SSAS Licensing and Infrastructure
Check out the Microsoft SQL Server 2014 Licensing Guide (PDF).

Page 11 says:


  The software components of a single SQL Server 2014 license cannot be separated for use in more than one OSE. If these components are running on a server other than the main database server, then an additional license is required for each additional OSE in which they are installed. For example, if the SQL Server DB is deployed in one OSE and SQL Server RS is deployed in another, both OSEs must be fully licensed for SQL Server 2014 accordingly.


What that means is that if you run the database engine, SSIS, and SSRS on three separate servers, then you have to license all three.