Hello Labingtone;
There are very few freebies in the Siemens world, and sofware licensing is not one of them. Yes, you will require a software license to run the driver you need (by the way, there are several Softnet drivers available for the CP5611; you need to determine the one you need, as each one requires a different licence authorization).
I you install the software without license you will get a Simatic Net message every time you try to communicate through the CP5611 and the operation will be blocked.
Hope this helps,
Daniel Chartier