What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
If you have used the JotForm URL to share it on your facebook page, the said text shall definitely appear and it's not possible to remove since it is by Facebook's practice to share the domain where the link is from as safeguard to spam and any form of malicious practice.
Perhaps what you can do is embed the form to your webpage and use that link of your page where the form appears to share to your facebook page. This way, what shall appear there is the link to your domain.