This is a very experimental, not complete, not fully functionnal, probably heavily bugged project. In fact, for the moment, this is closer to a proof of concept than an actual “usable” extension. But it works as long as you don’t stress it too much :).

Lightweight CalDAV+CardDAV server

Related contents:

• Baikal CalDAV Hosting @ My random ramblings

Open source push technology.

Z-Push is an open-source application to synchronize ActiveSync compatible devices such as mobile phones, tablets and Outlook 2013 and above. With a history of over 9 years of successful synchronization with multiple backends Z-Push is the leading open source push synchronization.

• Z-Push @ GitHub.

The open source CardDAV, CalDAV and WebDAV server.

Sabre.io @ GitHub

Open Source Groupware. SOGo is a fully supported and trusted groupware server with a focus on scalability and open standards. SOGo is released under the GNU GPL/LGPL v2 and above. SOGo provides a rich AJAX-based Web interface and supports multiple native clients through the use of standard protocols such as CalDAV, CardDAV and GroupDAV, as well as Microsoft ActiveSync.

CalDAV, CardDAV and WebDAV for Android.

Sync your contacts, calendars and tasks. Get live-access to your WebDAV Cloud files. All-in-one CalDAV/CardDAV/WebDAV solution for Android.

DAVx⁵ is an open-source CalDAV/CardDAV suite and sync app for Android. You can also access your online files (WebDAV) with it.

• DAVx⁵ @ GitHub.
• Episode 590: Self-Host Before You're Toast @ Linux Unplugged.

Baïkal is a lightweight CalDAV+CardDAV server. It offers an extensive web interface with easy management of users, address books and calendars. It is fast and simple to install and only needs a basic php capable server. The data can be stored in a MySQL or a SQLite database.

• Baïkal @ GitHub.

Related contents:

• Stop Uploading Your Data to Google @ ignore the code.
• Why Self-host? @ Roman Zipp.

A simple, fully translatable admin interface and frontend for sabre/dav.

Provides user edition, calendar creation and sharing, and address book creation. The interface is simple and straightforward, responsive, and provides a light and a dark mode.

Free and Open-Source CalDAV and CardDAV Server.

Radicale is a small but powerful CalDAV (calendars, to-do lists) and CardDAV (contacts) server.

• Radicale @ GitHub.

Secure Data Sync.

Secure, end-to-end encrypted, and privacy respecting sync for your contacts, calendars, tasks and notes.

Easy to use and open source - it seamlessly integrates with your existing apps so you won't even notice you are using it!

• EteSync server @ GitHub.
• etesync-dav @ GitHub is a CalDAV and CardDAV adapter for EteSync.