I agree with @AndersBGS - contact your account rep.

But in general I can tell you that ASSIGNING that role will not impact licensing costs, BUT when someone that you assigned it to then does a GRC action it will impact licensing costs.

The GRC Business User was introduced about a year ago. The idea is that there are tasks we need people outside the Compliance and Risk teams to perform.  If we give them a reader role, then they can't update a task. If we give them the compliance or risk user role; then they have too much power to edit things we don't want them to edit. And please be aware that there is now also a GRC Business User Lite role.

Check out the details in this product doc article:  https://docs.servicenow.com/bundle/utah-governance-risk-compliance/page/product/grc-policy-and-compl...

Here is a link to an article I wrote about a year ago - things have changed since I wrote this, but this is the basics:

https://www.servicenow.com/community/grc-articles/grc-business-user-role-v-12-x-new-updates-you-want...