Keeper.sh

Keeper.sh is an open source calendar syncing tool that pulls and pushes events between calendar sources and destinations. It works through iCal/ICS or OAuth and can synchronize anonymized busy/free events, allowing availability to be shared without exposing event details. It is intended for people who use multiple calendar sources and need to keep their availability synchronized while controlling how much information passes between calendars. No specific paid product is identified as a direct replacement for Keeper.sh. Its stated focus is calendar event synchronization through iCal/ICS or OAuth. When anonymized busy/free synchronization is used, the destination receives availability rather than the full details of each event. This protects private information, but it also means the synchronized calendar does not contain a complete copy of the original event data.