The problem is Formstack is dynamically adding its own version of jQuery, precisely this line:
document.write(" <script type=\"text/javascript\" src=\"http://www.formstack.com/forms/js/3/jquery.min.js\"></script>"+"\n");
That’s very poor coding that could potentially affect a lot of functionality not only the theme’s. There’s nothing I can do to make the theme compatible with that kind of coding and not break.