The best open source alternative to Formstack is Nextcloud Forms, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Formstack and seven of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Formstack are SurveyJS (Free Personal, Open Source), OhMyForm (Free, Open Source), EUSurvey (Free, Open Source) and ApPHP DataForm (Paid, Open Source).
📝 Simple design: No mass of options, only the essentials. Works well on mobile of course. 📊 View & export results: Results are visualized and can also be exported as CSV in the same format used by Google Forms.
Unlike the most others solutions, SurveyJS Project consists of three fully independent parts: run-time SurveyJS library, SurveyJS editor and SurveyJS service for storing and analyzing results. You may stick with the complete solution or use only a library.
OhMyForm is a free and open source alternative to commercial form creators like Typeform and Google Drive - Forms providing all the features you need to run, administer, analyze and distribute forms for free.
EUSurvey is supported by the European Commission to promote interoperability solutions for European public administrations. A hosted version is available free of charge to all EU citizens. Open-source, published under the EUPL licence.
ApPHP DataForm script is a simple tool for creating HTML forms with ease. It was especially designed for web developers, who do not want to spend excessive time on creating forms in HTML or through PHP, but want to use a first-class OOP backend.
FormBucket gives you a hosted endpoints for your static site forms. Your markup, your CSS. We take care of the rest. You can redirect users to any URL, send autoresponder emails and add unlimited webhooks.