Cal.com
Open Source Meeting Scheduling Software
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Focalboard
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Ghost
Publishing platforms for blogs, websites and newsletters.
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Project management for non-project managers
listmonk
Newsletter and mailing list manager
Mattermost
Open Source Platform for Secure Workplace Messaging
Nextcloud
A safe home for all your data
OpenProject
Powerful classic, agile or hybrid project management
Owncloud
A personal cloud which runs on your server.
Plane
Open-Source project management tool from the future
Rallly
Open Source scheduling and collaboration for organizing events and meetings
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Samay
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Seafile
File Sync & Share software with document collaboration features.
Zulip
The team chat that helps teams stay productive and focused