List of Top Free Open Source & Self Hosted Application for Calendar & Contacts - CalDAV or CardDAV Servers

CalDAV and CardDAV protocol servers Electronic calendar and address book and contact management.

Baïkal – Lightweight CalDAV and CardDAV server based on sabre/dav. GPL-3.0 PHP
calypso – Python-based CalDAV and CardDAV server, forked from Radicale. GPL-3.0 Python
DAViCal – Server for calendar sharing (CalDAV) that uses a PostgreSQL database as a data store. GPL-2.0 PHP
Davis – A simple, dockerizable and fully translatable admin interface for sabre/dav based on Symfony 5 and Bootstrap 4, largely inspired by Baïkal. MIT PHP
Etebase (EteSync) – End-to-end encrypted and journaled personal information server supporting calendar and contact data, offering its own clients. AGPL-3.0 Python/Django
Radicale – Simple calendar and contact server with extremely low administrative overhead. GPL-3.0 Python
SabreDAV – Open source CardDAV, CalDAV, and WebDAV framework and server. MIT PHP
Xandikos – Open source CardDAV and CalDAV server with minimal administrative overhead, backed by a Git repository. GPL-3.0 Python