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.
I needed to apply a new theme to the form to overwrite the background but you should be able to remove the gradient. Even removing all the CSS from the form would not allow me to remove it:
Clone it to your own account and you will be able to edit the background of the form and the background image without issue: