SSIS Standalone Installation In my organization we have several SQL Server 2016 Enterprise licenses in use.  None of them are running SSIS.  Since they are not in use, could I install just SSIS 2016 on a separate server and still be covered under the original enterprise license?
You can, but read this article on the implications of doing so.
https://docs.microsoft.com/en-us/sql/integration-services/install-windows/install-integration-services