DAVx⁵

CalDAV/CardDAV Synchronisation and ClientGPL-3.0-only

Tasks.org: Open-source To-Do Lists & Reminders

Private, ad-free task lists! Optional sync with Google Tasks, CalDAV or EteSync!GPL-3.0-only

Infomaniak kSync

Automatically sync your contacts and calendarsGPL-3.0-only

jtx Board journals|notes|tasks

Keep track of journals, notes & tasks - iCalendar compliant and syncable with yoGPL-3.0-only

Linwood Flow Nightly

Feature rich event, group and time management systemAGPL-3.0-only

OpenTasks

Open Source Task Management.Apache-2.0