Agorakit is an Open Source groupware for citizens to organize and collaborate online, facilitating communication, scheduling, and information sharing.

cal.com

Cal.com: The better way to schedule your meetings, offering a fully customizable experience for individuals and businesses.

DAViCal

DAViCal is an Open Source CalDAV server for secure and collaborative calendar sharing.

Dendrite is a high-performance, scalable, and reliable Matrix homeserver written in Go.

DumbDrop

DumbDrop is a straightforward file upload application that enables easy drag-and-drop file sharing without authentication or complex setup.

Etherpad MyPads is a self-hosted, real-time collaborative document editor for enhanced team productivity and secure document management.

Gokapi

Gokapi is a self-hosted, secure file-sharing server with admin-only uploads, file expiration, and cloud storage support.

Jangouts is a self-hosted, Open Source video conferencing solution using WebRTC and Janus Gateway.

Nextcloud Hub

Nextcloud Hub is a secure, integrated collaboration platform that combines file sharing, communication, and office tools for enhanced productivity and data control.

Nextcloud Social

Nextcloud Social is a collaborative app that adds social networking features to Nextcloud, fostering communication and engagement among users.

PlikShare

PlikShare is a self-hosted, secure file-sharing platform offering unlimited users and storage for a one-time payment.

ProjectSend

ProjectSend is a free, secure, and user-friendly self-hosted file-sharing application that enables easy and private file exchange with clients.

Open source alternative communication platform

ThreemaOnPrem

Threema OnPrem is a self-hosted, highly secure enterprise messaging solution providing total data ownership and control.

Tracim is an Open Source, all-in-one collaborative platform designed to streamline team communication, project management, and knowledge sharing.