If you use NPS for your product are you paying the license fee?

I was researching making a simple satisfaction survey tool that provided NPS, CES, and CSAT surveys. However, in my research I found out if you want to provide NPS in a commercial application you need to buy a license at $5,000/year. This obviously puts it out of reach for a lot of indiehackers, yet I feel like I see it all the time as a feature in tools posted here. Are these products just unaware and flying under the radar? Or am I missing something about the license terms?