SOGo - SOGo is groupware server with a focus on scalability and open standards.
Zen Planner - Zen Planner's fitness membership management software helps you grow your box, gym or studio with scheduling, automated billing & more. Try it now for free!
Baïkal - Cal and CardDAV server
Pike13 - Pike13 provides a mobile-first solution for "on-the-go" owners of small service business who are trapped in a paper world trying to manage their clients.
Xandikos - Lightweight CalDAV/CardDAV server on top of Git.
Glofox - Powerful Gym and Studio Management Software.