Gitea : Gitea is a community managed fork of Gogs, lightweight code hosting solution written in Go and published under the MIT license.
cal.com : Open source meeting scheduling tool. Send a link, let others book a slot. Calendly alternative.
Mattermost : Mattermost is a self-hosted solution for bringing all your team communication to one place, and making it searchable and accessible anywhere
Beanstalk : Code hosting for private teams.
Imagine a single process to commit code, review with the team, and deploy the final result to your customers.
GitLab is a web-based Git repository manager with wiki and issue tracking features. GitLab offers hosted accounts similar to GitHub, but also allows its software to be used on third party servers.