Bus Factor Score

Single author controls 100% of the codebase. No external PRs accepted. Code is public domain but development is closed.

Effectively unmaintained since 2021. Single maintainer moved to other projects. 50M+ weekly npm downloads with no active development.

One developer writes virtually all code. No governance structure. Popular (42k stars) but entirely dependent on a single person.

Carson Gross writes essentially all code. Wildly popular contrarian library. Bus factor 1 but scope is intentionally small and stable.

Single creator writes virtually all code. Bun-specific framework limits contributor pool. Popular (10k stars) but entirely dependent on one developer. No governance.

Paul Gauthier writes virtually all code. Highly opinionated single-person project. Python codebase, large user base. Bus factor 1 but development is rapid and consistent.

Felix Böhm wrote virtually all the code. 8M+ weekly downloads. Maintenance-mode since 2023. Foundational for Node.js web scraping but one person controls everything.

Fabian Hiller writes virtually all code. Growing alternative to Zod with smaller bundle. No corporate backer. Active development but entirely one person.

Pilcrow (solo developer) created and maintains it. Announced deprecation in favor of custom implementations. v3 was already bus factor 1 — now intentionally sunsetting.

Daniel Stenberg wrote 80%+ of all commits. Large contributor base for patches, but architectural decisions rest on one person.

Colin writes most core code. Very popular (30k stars, 20M+ downloads/week). Zod 4 rewrite is mostly single-person effort.

Ryan Carniato wrote the core and still makes almost all architectural decisions. Netlify sponsorship adds stability but project depends on one person's time.

Creator-led with small core. Rapidly growing (12k stars) but no corporate backer. Plugin architecture helps distribute work but core decisions flow through 1-2 people.

C++ core written primarily by the founder. Cloud revenue sustains development but core expertise is concentrated in 1-2 people.

Andras Bacsai writes the vast majority of core code. Growing contributor base but architectural decisions flow through one person. Revenue from cloud plan.

Ruben Fiszel writes the vast majority of code. Small team, seed-stage. Rust backend limits contributors. High expertise concentration risk.

Creator-led with few core contributors. No corporate backing. Popular in TypeScript ecosystem but maintenance depends on 1-2 people. Dialect plugins help distribute work.

Zoltan Kochan is the primary author and still writes most code. Teamwork.com pays his salary. If either changes priorities, pnpm loses its main maintainer.

Single primary maintainer (Damien Arrachequesne / 'darty'). Over 60M downloads/week. Mature and stable but essentially unmaintained for new features. New WebSockets APIs reduce relevance.

DongYoon Kang (강동윤) wrote essentially all of it. Vercel sponsors his work because Next.js depends on SWC. Bus factor 2 at best. Rust codebase limits contributors significantly.

Sasha Koss writes most core code. 25M+ weekly npm downloads. v3 rewrite mostly single-person effort. No corporate backer. Funded by GitHub Sponsors.

Sunil Pai created it and led Cloudflare acquisition. Small team at CF now maintains it. Cloudflare backing reduces risk but team is tiny.

Primarily Julius Marminge (julius) and a tiny team. Popular in T3 ecosystem. No standalone funding — depends on Ping Labs priorities. Simple scope reduces risk somewhat.

Andreas Thomas and James Perkins lead. Small team, growing but core architecture rests on 2 people. Open source with hosted cloud. VC-backed seed stage.

Anthony Fu created and maintains it along with dozens of other OSS projects. His output is legendary but unsustainable. If he burns out, a huge chunk of the Vite/Nuxt ecosystem is affected.

Lovell Fuller is the primary maintainer. 10M+ weekly downloads. Critical for Next.js image optimization. C++ bindings to libvips limit contributor pool significantly.

Sami Koskimäki wrote and maintains the core. Growing popularity as type-safe SQL alternative. No corporate backer. v1.0 approaching but development pace depends on one person.

Express 5 took 10 years. Governance exists on paper but development stalled for long periods. Foundation backing didn't prevent maintainer burnout.

Adam Wathan and a small core team. Well-funded through Tailwind UI revenue but knowledge is concentrated in 2-3 people.

Rich Harris joined Vercel to work on Svelte full-time. Core design decisions still flow through him. Community contributors handle periphery.

Small funded team. Alex Blokh leads. Growing contributor base. Revenue from Drizzle Studio sustains development.

Jarred Sumner writes vast majority of Zig code. Funded by Oven but Zig expertise is rare. Core runtime deeply tied to founder.

Yusuke Wada drives development while employed at Cloudflare. Growing contributor base but architecture decisions flow through the creator. No formal governance.

Alex KATT (Alex Johansson) wrote and maintains the core. Small team. v11 rewrite stretched resources. No corporate backer. Sponsored via GitHub Sponsors.

Zeno Rocha leads. Small team but funded and focused. SDK is simple (low complexity = low bus factor risk). Core email infra is the real dependency.

Michael Arnaldi and small core team. Functional programming expertise limits contributor pipeline. VC-backed but niche adoption. Complex codebase = high barrier.

Tobie Morgan Hitchcock leads. Rust core with small expert team. Ambitious multi-model scope means high expertise requirement. Funded but small.

Misko Hevery (Angular creator) leads. Builder.io funds development. Small core team but corporate backing reduces risk. Innovative architecture limits casual contributors.

Small funded team. Core development concentrated in a few people. Svelte frontend. Growing but still dependent on core team for architectural decisions.

Thinkmill agency maintains it. Small core team. Development pace has slowed significantly. Prisma dependency adds complexity. Competing with faster-moving alternatives.

Started by Saoud Rizwan. Active community contributions. Apache 2.0 license. Growing core team. Competing with well-funded proprietary tools.

Birk Jernström leads. Small funded team. Apache 2.0 OSS payments + commercial MoR service. Niche bet against Stripe. Code accessible but core dev concentrated.

Kamil Mysliwiec wrote and maintains the core from his consulting company Trilon. Very popular in enterprise TypeScript backend space. No major corporate sponsor. Consulting revenue funds development.

Vladimir Sheremet leads. Anthony Fu and Vite core team involved. No standalone funding but Vite's success sustains contributors. Replacing Jest rapidly in modern frontend stacks.

Small rotating core team. James Long created it; Christopher Chedeau popularised it at Facebook. Biome and dprint are faster alternatives. Core is very stable — low likelihood of urgent changes needed.

Tobias Koppers dominates commits. In maintenance mode — new projects use Vite/Rspack/Turbopack. Critical for millions of legacy projects but development is winding down intentionally.

Boshen Chen leads. VoidZero (Evan You's company) funds it. Part of the Rolldown/Vite next-gen toolchain. Pre-1.0 — small team but well-directed. Evan You's company backing adds credibility.

James Arthur leads. Small funded team building Postgres sync engine. Pivoted from full ORM to thin sync layer in 2025. Early stage with concentrated expertise.

Daishi Kato maintains Zustand, Jotai, and Valtio simultaneously. Poimandres collective provides some shared governance. 45M+ monthly npm downloads. One person, three major state libraries.

Evan You writes most core code. Growing team but architectural vision depends heavily on one person. Funded by sponsors and consulting.

Taylor Otwell controls direction and writes most core code. Large ecosystem but framework vision is single-person. Revenue from Forge/Vapor/etc.

Key subsystems have single maintainers. Messy governance history (Libav fork). Core contributors are aging out without replacements.

Funded company with growing team. Core architecture shared across 4-5 engineers. Open source SDK, proprietary orchestration engine. Typical startup risk profile.

Rose from Rome's ashes with a new governance model. Core team of 4-5 active contributors. Rust codebase limits contributor pool. Growing but still fragile.

libSQL fork of SQLite with a funded team. Core contributors are few but paid full-time. Chiselstrike pivot to Turso shows adaptability.

Funded company. SDKs are maintained by a small team. Core Redis/Kafka infrastructure is proprietary. Team is small but stable.

Funded team with growing contributor base. v2 rewrite concentrated knowledge in core team. Open source reduces risk — community can fork.

Elvis Pranskevichus and Yury Selivanov co-founded. Python and Rust codebase. Small team but technically deep. Niche adoption limits contributor growth.

Andrey Vasnetsov leads. Rust core with growing team. Funded and focused on vector search niche. Small but active contributor base.

CNCF graduated but development pace slowing. Yuri Shkuro originally led. OpenTelemetry Collector is absorbing Jaeger's role. Maintenance mode risk.

GitHub co-founder backs it. Core team of 5-6 people. Community has contributed significantly but architectural decisions flow through core. RSC migration is a major effort.

Funded team with growing contributor base. Open source with active community. Core team drives architecture but community contributes connectors and components.

Steven Fabre and Guillaume Salles co-founded. SDK is OSS, server proprietary. Small focused team. Growing in collab tools market.

Matteo Collina leads and is also a Node.js TSC member. Nearform sponsorship provides stability. Community-driven governance. Smaller team than NestJS but technically deeper.

Part of Vite's next-gen toolchain. Rust rewrite of Rollup funded by VoidZero. Small team but Evan You's track record and funding provide stability. Pre-1.0 with rapid development.

Small funded team building v3 rewrite. Matt Aitken leads. Open source SDK with proprietary cloud. Typical early-stage startup risk profile.

Pooya Parsa leads. Powers Nuxt, Analog, and other frameworks. NuxtLabs funding provides stability. Growing adoption outside Nuxt ecosystem reduces single-framework dependency.

Foundation governance with CrabNebula providing commercial support. Daniel Thompson-Yvetot leads. Rust codebase limits contributor pool but community is active and growing.

Built on libSQL fork of SQLite. Glauber Costa leads. Small team but well-funded. Edge database use case is growing. Risk is startup economics, not maintainer loss.

Moved to dual-license (RSALv2/SSPL) in 2024. Company-controlled. Forks (Valkey, KeyDB) exist as hedges. Salvatore Sanfilippo stepped back in 2020.

Funded company with dedicated team. Fred K. Schott leads but team is distributed. Active contributor base beyond core team.

Acquired by Shopify in 2022. Shopify backing reduces financial risk but corporate priorities could shift. Core team is small but paid full-time.

Rich Harris and core Svelte team work at Vercel. SvelteKit has broader contributor involvement than Svelte core. Vercel backing reduces bus factor risk significantly.

Funded team with growing contributor base. James Mikrut leads but development is distributed. Payload 3.0 rewrite brought in new contributors.

Well-funded company with experienced engineering team (ex-Dropbox). Core backend is proprietary — bus factor matters less when it's a product, not a volunteer project.

Vercel employees maintain it. Rust codebase means high barrier for community contributions. Tightly coupled to Next.js — Vercel won't abandon it.

Funded company with a dedicated Rust team. Cloud product funds development. Bus factor is reasonable for the team size.

Well-funded company with large engineering team. BSL license means MapLibre is the community fork. Core development is company-driven.

Enterprise company with dedicated SDK teams per language. Well-funded. SDKs are OSS, platform is proprietary SaaS.

Ben Haynes leads. Funded company with growing team. Active community contributors. Database-first approach means less custom code to maintain.

Well-funded with large contributor base. Peer Richelsen leads but development is well-distributed. AGPLv3 means community can always fork.

Joe Duffy co-founded. Funded company with growing team. Go/TypeScript core. Multi-language support means distributed expertise across runtime teams.

Funded company with dedicated PostgreSQL experts. C codebase (PostgreSQL extension). Small but specialized team. Ajay Kulkarni co-founded.

Terraform fork under Linux Foundation. Multiple companies contributing (Spacelift, env0, Scalr). Growing maintainer pool but still catching up to Terraform's depth.

Well-funded with a dedicated engineering team. Active open-source community. Distributed commit history. TypeScript/React codebase accessible to contributors.

Non-profit foundation with sustainable revenue. John O'Nolan founded but team is distributed. Node.js codebase. Mature and stable. Community contributes themes and integrations.

Closed source. Engineering team is small relative to user base. Michael Truell co-founded. Heavily VC-funded. Risk is competitive — fast-moving AI tooling space.

Jorge Sancha and team. Built on top of ClickHouse — leverage existing OSS. Funded with growing team. Cloud product is the moat.

Vercel acquired from Jared Palmer in 2021. Rust rewrite by Vercel team. Tightly coupled to Vercel's monorepo tooling story. If Vercel deprioritises, Nx takes the market.

NuxtLabs is a commercial entity behind Nuxt. Revenue from Nuxt UI Pro and consulting. Daniel Roe and Sébastien Chopin lead. Active contributor base in Vue ecosystem.

OpenJS Foundation governance. Nicholas Zakas created it but team has grown. Corporate sponsors (Microsoft, Airbnb, Google) fund ongoing work. v9 flat config migration stretched team.

ByteDance team of 10+ engineers. Rust-based webpack-compatible bundler. Corporate backing is strong but if ByteDance deprioritizes, community alone may not sustain the pace.

DHH still influential but commit share is distributed. Rails Foundation formed 2022 with Shopify, GitHub, etc. Mature governance.

Ryan Dahl founded the company but day-to-day development is distributed across a dedicated team. Commercial focus on Deno Deploy creates sustainability.

VC-funded company with dedicated engineering team. Johannes Schickling drives vision. Prisma Accelerate/Pulse are revenue plays. If funding runs out, risk rises.

Jan Oberhauser founded. Growing company with distributed team. Large contributor base builds community nodes. Revenue-funded and growing.

Well-funded with dedicated OSS team. Lua/OpenResty core. Large plugin ecosystem has external contributors. Mature governance.

Similar story to Vault — BSL license, IBM acquisition. Development pace has slowed. Community engagement declining. Still maintained but future unclear.

Grafana Labs funded. Go codebase. Active development with multiple maintainers. Part of the broader Grafana observability stack.

Proprietary platform — OSS components are minimal. Company went through layoffs in 2023. Bus factor is about company health, not individual contributors.

CNCF graduated with multiple corporate sponsors (Intuit, Red Hat, Codefresh). Distributed maintainership. Active contributor base across many companies.

Well-funded AI infrastructure company. Large team of ML engineers. Open-source model contributions but core platform is proprietary. Multiple co-founders distribute knowledge.

Large team at Vercel dedicated to Next.js. Broad contributor base. Risk is corporate priority shifts, not maintainer loss.

Well-funded VC-backed company. Large distributed team. Open source core means community can fork. Risk is startup failure, not individual contributor loss.

Well-funded company with a large engineering team. Core is PostgreSQL fork — deep DB expertise required. Well-distributed commit history.

Maxim Fateev and Samar Abbas co-founded. Large engineering team. Go codebase is well-structured. Very well-funded enterprise company.

Well-funded with dedicated engineering team. Originally Yandex project — distributed knowledge from the start. C++ core limits casual contributors but team is large.

Large contributor base historically. BSL license change reduced community contributions. IBM acquisition adds corporate uncertainty. OpenTofu fork drew some maintainers away.

Large team historically. BSL license change. IBM acquisition. OpenBao fork exists. Core team is paid full-time. Go codebase.

SUSE-owned with a large engineering team. Darren Shepherd co-founded. Distributed commit history. K3s/RKE2 have separate maintainer teams.

One of the oldest CI/CD tools with massive contributor base. Plugin system distributes maintenance. Kohsuke Kawaguchi created it but stepped back. Community governance.

Evan You created it but core team is wide (Anthony Fu, Patak, Bjorn Lu). De facto frontend dev tool. Rolldown migration concentrates expertise but team is large.

Redis fork after RSALv2/SSPL license change. Multiple corporate maintainers. Madelyn Olson (AWS), Viktor Söderqvist active. Strong governance from day one.

Microsoft-backed team. Dmitry Gozman and Arjun Attam lead. Part of VS Code ecosystem investment. Large Microsoft team dedicated to it. Replaced Puppeteer as standard browser automation.

Arthur Mensch co-founded. Massive European AI company with large engineering team. Open-weight models reduce dependency risk. Revenue from API and enterprise.

Large Meta team. Andrew Clark, Sebastian Markbage, etc. Risk is Meta deprioritizing, not individual departures. MIT licensed.

Large engineering team with distributed commit history. Spencer Kimball co-founded. Well-funded with enterprise revenue. Go codebase.

CNCF graduated with broad industry backing. Multiple companies contribute. Well-distributed maintainership across subsystems. De facto metrics standard.

Large team at Elastic. Tightly coupled to Elasticsearch. Revenue-funded. TypeScript/React frontend. Broad contributor base.

Microsoft TypeScript team is large and dedicated. Anders Hejlsberg originally designed it. Go port announced 2025 shows continued investment. Corporate future-proofing — not going anywhere.

Public company with large engineering team. Revenue-funded development. Hundreds of active contributors. Return to AGPL restored community contributions.

Public company with hundreds of engineers. Highly distributed commit history. Open core model means community has access to CE. No single person dependency.

Google Angular team is large. Angular CLI, CDK, Material all actively maintained. Risk is Google kills it (AngularJS precedent) but Angular v2+ is too embedded in enterprise to abandon.

Most distributed project in history. Subsystem maintainer model. Linus is a bottleneck only for merge decisions, not code.

Decades of distributed governance. No single company controls it. Committer process is meritocratic. Gold standard for OSS governance.