LimeSurvey (formerly PHPSurveyor) is an Open Source PHP web application to develop, publish and collect responses to online & offline surveys. Anonymous and Not-Anonymous survey, open and closed group of participant surveys, optional public registration for surveys. More than 50 different languages in frontend and backend. LimeService is a survey service-platform to prepare, run and evaluate on-line surveys. Besides basic free usage you are always getting the full feature set with no monthly fees or subscription plans: https://www.limesurvey.org/
We recently started using Luumy for our business. To be fair the engagement ratio is great, and the developers are super hands-on.
I would recommend supporting this product, and I can't wait to see where development takes it! +1!