broadinstitute/viral-ngs

New Expensify is an open-source rebuild of the popular expense management app, redesigned from the ground up around chat and real-time financial collaboration between teams. Instead of treating expense tracking as a back-office chore, it weaves money management directly into conversations, making it feel more like a messaging app than traditional accounting software.

why it matters: With nearly 5,000 stars and over 2,300 contributors, this project signals that Expensify is betting its future on a chat-first, collaborative financial workflow — a direct challenge to legacy tools like Concur and even newer players like Brex or Ramp. For founders and PMs, it's a live case study in how an established fintech company is open-sourcing its core product to accelerate development and build community loyalty while repositioning against a rapidly evolving competitive landscape.

Cataclysm: Dark Days Ahead is a free, open-source survival game where players navigate a post-apocalyptic world filled with zombies, monsters, and the remnants of civilization — scavenging for food, weapons, and vehicles to stay alive. The game world is procedurally generated (meaning it's randomly created each time, offering endless replayability) and runs entirely in turn-based mode, giving players time to think through every decision.

why it matters: With nearly 13,000 stars and almost 3,000 contributors, this project demonstrates the massive scale and longevity that open-source games can achieve without traditional publishing or monetization models — a useful case study for anyone building community-driven products. Its deep modding ecosystem and passionate contributor base also make it a reference point for how to sustain long-term engagement in entertainment software.

First Contributions is a guided learning project that walks complete newcomers through the process of making their very first contribution to a shared software project on GitHub, available in dozens of languages. It provides a safe, low-stakes environment where people can practice the collaboration workflow used by millions of software teams worldwide.

why it matters: With over 17,000 contributors and 105,000 forks, this is one of the most widely used onboarding pipelines for new developers entering the open-source ecosystem — meaning it shapes the habits and tooling preferences of the next generation of builders. For companies investing in developer communities, open-source strategies, or talent pipelines, this project represents a significant entry point into how future engineers learn to collaborate.

This repository contains the official user manual and reference guides for Godot Engine, a free and open-source tool for building video games that runs on multiple platforms. The documentation covers everything from getting started to advanced game-building techniques, and can be read online or downloaded for offline use.

why it matters: Godot is one of the fastest-growing alternatives to expensive commercial game engines, and with nearly 1,900 contributors to its documentation alone, it signals a massive and active developer community rallying around an open-source option. For founders and investors, this represents a shift in the game development market where indie studios and small teams can build professional games without licensing fees, lowering barriers to entry and enabling new business models.