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.
Unfortunately, we do not have a feature or widget that allows you to directly feed a drop down field on JotForm from a text file as a source. You'll need to manually add the list of items in your form.
We do have some drop down widgets that you can check. You can search them on this page: http://widgets.jotform.com/. We have the "User Contributed Drop down" widget that allows your users to add an option in the drop down field.
Another possible way is to use the form's full source code, create a custom script that will prepopulate your options list from a text file source. However, you'll need to embed the form's source code on a web page/server and you'll need to develop or hire a developer that will create the custom script.
Here are some discussions about it: http://stackoverflow.com/questions/14857054/populating-drop-down-menu-from-comma-delimited-text-file?answertab=active#tab-top.
You can try loading the text file using JSON.
I hope that helps.