Teams that cannot send messages through someone else's cloud run Mattermost - the open-core, self-hosted alternative to Slack. It provides public and private channels, threaded discussions, unlimited search history, file sharing with previews, one-to-one audio calls, and screen sharing, with desktop clients for Windows, macOS, and Linux plus iOS and Android apps. Messages support full Markdown, which suits engineering conversations with code blocks and logs. Playbooks turn repeatable processes such as incident response and release management into checklist-driven workflows with automated triggers and retrospectives. Integration is a core strength: prebuilt connectors for GitHub, GitLab, Jira, ServiceNow, and PagerDuty, plus webhooks, slash commands, bots, a REST API, and a plugin marketplace with 700+ entries - together making it a working surface for ChatOps rather than just a chat room. Playbooks add keyword and event triggers, task assignment, status broadcasting, and post-incident retrospectives, so operational knowledge is not trapped in individuals' heads. The server is a single Go binary backed by PostgreSQL, with React clients, released monthly under MIT license and deployable fully air-gapped - which is why governments and defense organizations run it inside closed networks, and why the same control applies to any team with confidentiality requirements. The compiled Team Edition is free for unlimited users with no message history cutoff, so costs stay flat as the team grows.

Used by the Rust language community, NASA, Dropbox, and thousands of organizations worldwide with over 25,600 GitHub stars and 1,500+ contributors, Zulip is the only modern team chat app designed from the ground up for both real-time and asynchronous communication through its unique topic-based threading model where every message belongs to a named topic within a channel. This eliminates the context collapse of linear chat by letting teams follow specific conversations without scrolling through unrelated messages, resume threads days later without losing context, and catch up on missed discussions at per-topic granularity. Server 12.0 introduced end-to-end encryption for mobile push notifications, AI-powered search ranking, channel folders for workspace organization, and expanded video conferencing with Jitsi, BigBlueButton, and Zoom integration. Over 100 native integrations connect GitHub, GitLab, Jira, Sentry, PagerDuty, Travis CI, Redmine, dbt, Nextcloud, and n8n with bidirectional notifications, while LLM-driven agents access web-public channels via a standard llms.txt interface. Full-text search covers unlimited message history across all plans, code blocks render with syntax highlighting for 250+ languages, and LaTeX math expressions display inline. The REST API with typed Python and JavaScript SDKs enables custom bots, webhook integrations, and programmatic administration. Import tools migrate entire workspaces from Slack, Microsoft Teams, Mattermost, and Rocket.Chat. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

With over 10,000 GitHub stars and a reputation forged in the frustration of laggy corporate screen sharing, Screego delivers what Microsoft Teams and Zoom screen share consistently fail to provide: instant, high-resolution screen streaming that lets remote colleagues actually read your code. Built on WebRTC peer-to-peer connections, Screego transmits screen data directly between browsers without routing through centralized servers, achieving sub-second latency and native-resolution quality that makes pair programming and code reviews genuinely productive. The server component, written in Go with a TypeScript frontend, deploys as a single binary or Docker container with minimal configuration — set your external URL, generate a secret key, and you're live. An integrated TURN server handles NAT traversal automatically, eliminating the need for separate STUN/TURN infrastructure, with configurable UDP port ranges and support for external TURN servers when scaling beyond a single instance. Authentication supports three modes — requiring login for all actions, only for TURN connections, or none — with user management via simple credential files. Rooms are created instantly and support multiple simultaneous viewers, with system and tab audio sharing available for demonstrations that need sound. The architecture supports reverse proxy deployment behind Nginx, Caddy, or Apache with automatic TLS termination, and recent releases added riscv64 architecture support alongside existing amd64 and arm64 builds. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

SealSkin is a self-hosted browser isolation platform that runs desktop applications in isolated containers on your server and streams them to any browser or phone, so links, files and downloads open remotely and nothing from the web ever executes on the device in front of you. Right-click a link, send a download, or drop a file from your local browser through the extension, and it opens in a fresh container on the server; close it and nothing is left behind, or keep a persistent home directory for work you return to. The catalog holds more than a hundred applications: browsers, office suites, IDEs, media editors, emulators and 3D tools from LinuxServer.io images, plus any Selkies-compatible image you add, with NVIDIA and DRI3 GPU acceleration for demanding workloads. Files stay on the server behind a file manager with chunked uploads, intercepted downloads, and password-protected public share links. Launch any app into a collaboration room with chat, voice and video, gamepad slots, and hand-over of mouse and keyboard control. Administrators brand the web app, manage users, groups, application keys, VPN profiles, and audit logs, and can route a session out through a WireGuard or OpenVPN exit at launch. Servers cluster with shared users and applications and no master node, and one manifest runs the whole thing on Kubernetes. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MPL-2.0 licensed.