Kin - Kin is money for the digital world. It is used to generate value through a shared, decentralized cryptocurrency in a digital ecosystem of apps and their users.
Cron - Cron Calendar.
BusyContacts - BusyContacts is a contact manager for macOS.
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
Plan - Plan is a better way to organize.
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.