LimeSurvey
Run branching, multilingual surveys on your own PHP server under the GPL, or in the vendor's cloud, which is priced by the number of responses you collect.
// SURVEY
4 entries tagged with "survey"
// COMPARISONS
1// ENTRIES
3 entries
OpnForm
Typeform-style forms on your own server with no cap on responses. The free self-hosted edition allows two accounts per instance; a paid license lifts the limit.
Formbricks
Surveys triggered inside your app or on your site by a click, page view or exit intent. Self-hostable AGPL core; segments, SSO and 2FA need a paid license.