For SQL Server 2005 and 2008 R2, the only way to get the Integration Services development environment, Business Intelligence Design Studio a.k.a. BIDS, was through the installation media aka you already bought Developer, Standard or Enterprise Edition. However, if you're looking to purchase SQL Server for the first time, it'd be insane to spend that level of money on an older version that is due to be retired in less than four years
2012 allowed you to install the design studio, rebranded as SQL Server Data Tools-BI edition or simply SSDT-BI, either from the installation media or you could download it directly from MS for free. See also
2014 and presumably 2016, the only way to get the SSIS development tools is to download directly. Again, no payment required, nothing. Just download and develop awesome business intelligence items.
But you're only licensed for development. You can't do things that are supporting production as that's part of the click through license agreement no one reads.
That should get SSIS set up and running via Visual Studio/SSDT/BIDS for nothing in your environment. There's no need to install an actual database, beyond wanting to evaluate it. Honestly, for that purpose, install SQL Express. It's free, handles up to 10GB as of current version and never expires.
My two bits on the Evaluation Edition is to never install that monstrosity unless you are planning on paving over the operating system at a later date. At a client, they have a licensed 2008 install and some one had the bright idea to install 2008 R2 evaluation edition on the same physical box. Due to the shared nature of 2008 and 2008 R2 libraries, the only thing that works on that box is the database engine itself. Attempt to access any of the tooling results in an expired license error message. The uninstaller can't uninstall 2008 R2 components because they're also shared by 2008... While a bit of rant, be cautious with the expiry nature of the evaluation edition. For SSIS, it will be overkill.