Is the Narrative Web Form Builder app available at an additional cost?

Is the below application available at additional cost? If not how do Integrate with an existing form?

Narrative Web Form Builder

Just to confirm are you referring to the Narrative Web Form Builder App? If so, then no, you won't be charged for using an app or a widget. The only time you will be charged by JotForm is if you have a paid subscription, which you currently have, a Silver Plan subscription.

Other than that, you shouldn't be charged elsewhere. Just go to the link above if you want to use the app, and if you stumble upon an issue along the way, open a new thread so we can assist you.