Tag
Source-available developer tools
Readable source, not OSI open source. 18 reviewed tools: 16 free or open source, 2 hosted with a real free tier.
Order: free and open source first, then hosted products with a real free tier, then paid-led; catalog order inside each group, with quiet or archived repos last. Not a score, and no tool pays for its place.
18 tools
- RedisThe in-memory data store everyone uses
Free / OSS · RSALv2/SSPLv1/AGPLv3 · 77k GitHub stars
VerdictThe default choice for caching and session storage.
CatchLicense: not MIT. Since Redis 8 the server is tri-licensed RSALv2 / SSPLv1 / AGPLv3 at your choice — AGPLv3 is the only OSI option and carries network copyleft; 7.4–7.x was RSALv2/SSPLv1 only. If you need BSD-3 Redis-protocol, look at Valkey. Memory-bound storage is expensive at scale. Persistence options have tradeoffs. Clustering adds complexity.
- CrushCharm-grade TUI coding agent with LSP and mid-session model switch
Free / OSS · Open-Core · 28.7k GitHub stars
VerdictThe beautiful, model-flexible TUI coding agent. Charm quality.
CatchLicensed FSL-1.1-MIT (competing-use restriction; source-available; MIT after two years—not OSI open-source). Pre-1.0 energy—config is migrating from JSON to crushrc Bash. Not a fully autonomous SWE agent like OpenHands; you stay in the loop. Hyper is Charm own model path if you want a subscription. Metrics on by default (DO_NOT_TRACK / CRUSH_DISABLE_METRICS to opt out).
- n8nFair-code workflow automation you can self-host
Free / OSS · Open-Core · 208k GitHub stars
VerdictThe workflow engine with a catch in the LICENSE.md. SUL, not OSI.
CatchSustainable Use License is not OSI. Use and modification: internal / non-commercial / personal. Distribution only free of charge for non-commercial purposes. Files with .ee. in the name need a separate Enterprise License. It is not open source.
- DefoldSource-available Lua game engine; forever free, not OSI Open Source
Free / OSS · Open-Core · 6.4k GitHub stars
VerdictForever-free Lua engine. Source-available — not OSI OSS; do not ship it as your own engine product.
CatchSource-available NOT OSI Open Source — §4a may not commercialize as a Game Engine Product. Forever free for making games; license is not MIT/Apache. Vs Phaser/melonJS/KAPLAY JS engines. Distinct from Phaser, melonJS, and KAPLAY.
- Invoice NinjaELv2 source-available invoicing; self-host free, hosted Free 5 clients
Free / OSS · Open-Core · 10.3k GitHub stars
VerdictELv2 invoicing. Self-host free for your biz; hosted Free 5 clients / Pro paid.
CatchNOT OSI open source — ELv2 forbids offering it as competing hosted SaaS. Hosted Pro from ~$14/mo (2026 pricing). Vs Lago/Autumn: client invoicing, not usage metering/MoR. Attribution stays unless white-label.
- SurrealDBBSL multi-model DB; free to use, not OSI open source
Free / OSS · Open-Core · 33.2k GitHub stars
VerdictBSL multi-model DB. Free for most builders; source-available with a DBaaS ban — say so out loud.
CatchBusiness Source License 1.1 — NOT OSI open source. You may not offer SurrealDB as a commercial DBaaS without a deal; code flips to Apache-2.0 after the change date (3.0 → 2030-01-01). Enterprise HA/security features are paid. It is not MIT/Apache OSS.
- gawkbotSource-available always-on bots that build microapps — local Grok Bot alternative
Free / OSS · Open-Core · 1.5k GitHub stars
VerdictSource-available local Grok Bot. Approval-gated personal bots; check SUL before you ship it as a product.
CatchSustainable Use License — source-available, not OSI open-source; read the license before commercial redistribution. Vs OneCLI / AgentBox / Dexto: gawkbot is personal always-on bots + microapps, not a team credential gateway or Elastic-licensed harness. You still bring a signed-in coding agent CLI and model spend. Per-bot VM computers are still on the roadmap per README.
- DextoElastic-2.0 agent harness OS — state, tools, recovery, ships a coding agent
Free / OSS · Open-Core · 652 GitHub stars
VerdictSource-available agent harness with a coding agent. Elastic-2.0 OS layer; not MIT and not a secrets gateway.
CatchElastic License 2.0 — source-available; SaaS/managed restrictions apply, not Apache/MIT freedom. Vs OneCLI / AgentBox / Mastra / VoltAgent: Dexto is the Elastic harness+coding-agent bundle, not the team credential gateway, sandbox host, or typed TS framework. Beta badge — treat APIs as moving.
- Context ModeElastic-2.0 MCP sandbox for tool output and session continuity
Free / OSS · Elastic-2.0 · 30.8k GitHub stars
VerdictElastic-2.0 source-available context middleware. Useful SQLite/FTS MCP sandbox; no hosted/managed offering without a careful license review.
CatchElastic License 2.0 is source-available, not OSI open-source; do not treat the `open-source` label as MIT/Apache freedom. ELv2 restricts offering the software as a hosted or managed service, so review the license before embedding or commercializing a managed Context Mode deployment. Vs a plain MCP server: this is output/context infrastructure, not another domain tool.
- Weave RouterELv2 on-box embedder proxy that routes each prompt to the right model
Free / OSS · Open-Core · 5.6k GitHub stars
VerdictELv2 source-available model router. Strong cost lever for agent fleets; no managed offering without a license review.
CatchElastic License 2.0 is source-available, not OSI open-source — you may not offer Weave Router as a hosted/managed service under ELv2 without permission. Vs LiteLLM: LiteLLM is the broader multi-provider gateway/SDK; Weave Router's wedge is per-prompt model selection via on-box embeddings. Routing quality still depends on your traffic mix and evaluation.
- tregMetered tool catalog and team vault for agent integrations
Free / OSS · Apache-2.0+Terms · 5.8k GitHub stars
VerdictSelf-host-free tool catalog with a serious license rider. Useful for a team that wants metering and vaulting; stop for legal review before embedding or offering it as a competing service.
CatchVs Composio and Smithery: treg is the self-hostable tool catalog and team-vault path, not a hosted connector marketplace or MCP registry alone. The Apache-2.0 license has additional terms — no competing hosted, managed, or embedded third-party service without prior written authorization — so it is not a clean “use the code anywhere” Apache grant. The curl|sh installer and credential injection deserve a disposable first run, pinned source, and narrowly scoped secrets.
- MulticaSource-available board where coding agents pick up human issues
Free / OSS · Open-Core · 53.1k GitHub stars
VerdictSource-available human+agent board when you want issue pickup across many coding CLIs in-house — read Part I before you SaaS it.
CatchVs Whiteboard / Pizza Bot: Multica is an agent task board/control plane, not a design canvas or inbox. Multica License = Apache-2.0 + Part I extras — hosting for third parties, public free instances, and commercial embedding need a producer license (Index Labs). Not OSI-clean Apache alone.
- NavopNative ops workspace (Apache-2.0 + Navop License rider) — DB, SSH, RDP, terminals, AI agents
Free / OSS · Apache-2.0+NAVOP_LICENSE · 1.9k GitHub stars
VerdictSource-available (Apache-2.0 + Navop License) native ops+AI workspace when DB/SSH/RDP belong in one GPUI app — not a thin SSH-only client, not Tabby.
CatchLicense: not a clean Apache-2.0 grant. NAVOP_LICENSE bans selling/reselling/paid redistribution, bundling into commercial products, paid download hosting, building competing products or services from its code, reverse engineering, and military use — free-channel redistribution only. Treat it as source-available. Vs Submarine (focused SSH/SFTP client): Navop is the broader ops+AI workspace. Vs Tabby (self-hosted coding assistant): Tabby is a local coding LLM product; Navop is connection/ops UI with agent features. Young native app — treat remote-desktop and AI connectors as maturing; verify release channel for your OS.
- Arize PhoenixELv2 self-host AI observability & eval — traces, datasets, playground
Free / OSS · Open-Core · 11.9k GitHub stars
VerdictELv2 self-host AI obs/eval when Phoenix’s tracing+evals fit and you accept source-available — not Langfuse MIT, not Braintrust CI-eval.
CatchNOT OSI open source — ELv2 forbids offering Phoenix as a competing hosted SaaS. Vs Langfuse (MIT full-stack self-host) and Braintrust (eval-first freemium): Phoenix is Arize’s ELv2 observability/eval kit with strong notebook/embedding UX, not MIT and not Braintrust’s CI-eval product. Arize cloud is the upsell when you want managed multi-tenant.
- Open WebUISource-available Ollama/OpenAI chat UI — RAG, tools, multi-user
Free / OSS · Open-Core · 156k GitHub stars
VerdictSource-available Ollama/OpenAI chat UI when polished local RAG chat beats building one — branding rules are the Catch vs LibreChat MIT.
CatchBranding lock — removing “Open WebUI” marks is forbidden above ~50 end users / 30 days without written permission or enterprise license (not OSI MIT/Apache). Vs LibreChat (MIT Agents/MCP/skills orchestration UI): LibreChat leans Agents/MCP/skills; Open WebUI leans Ollama-first chat+RAG+admin. You still BYO models, GPU, and upgrade discipline.
- RestateBUSL durable execution engine; self-host free, Apache after 4 years
Free / OSS · Source-available · 4.6k GitHub stars
VerdictDurable execution in one binary, free to self-host for your own apps; just do not resell it as a hosted Restate.
CatchLicense first: the server is under the Business Source License 1.1, which is source-available, not OSI open source. You can self-host it for free and use it in production for your own services and workflows, including an internal platform for your company or a public product that wraps it behind your own UI, DSL or API. What you cannot do is run a public managed service where outside developers register their own services and call Restate's APIs directly. Each release turns into Apache-2.0 four years after it ships. The SDKs are MIT. Upgrades need care (1.8 requires every node on 1.7.3 or newer first and a one-time partition migration), and it is a smaller ecosystem than Temporal. Check Restate Cloud pricing on restate.dev.
- InngestBackground jobs and workflows with zero infrastructure
Free tier · Source-available · 6k GitHub stars
VerdictThe missing piece for serverless background processing.
CatchLicense first: the Inngest server is under SSPL v1.0, each version converting to Apache-2.0 three years after release — source-available, not OSI open source today. The SDKs are licensed separately. Another service dependency. Debugging distributed workflows requires understanding the execution model. Costs scale with function runs.
- SentryError tracking that actually helps
Free tier · Source-available · 45.6k GitHub stars
VerdictThe error tracking service most teams use.
CatchLicense first: Sentry is under FSL-1.1 (Functional Source License, converting to Apache-2.0 after two years) — source-available, not OSI open source; you may self-host for your own use but not offer a competing service. Event volume drives cost. Self-hosting is complex. Some features are enterprise-gated. Alert noise requires tuning.
FAQ
- What is the top free pick among Source-available developer tools?
- Redis leads the Stack Gems list for Source-available developer tools. Verdict: The default choice for caching and session storage.
- How many Source-available developer tools does Stack Gems review?
- 18: 16 free or open source, 2 hosted with a real free tier. Each review has a verdict and an honest Catch; no tool pays for its spot.
- Which Source-available developer tools can I self-host for free?
- Redis, n8n, Invoice Ninja, SurrealDB, treg, Multica, Arize Phoenix, Open WebUI and 1 more.
- Which Source-available developer tools have the most GitHub stars?
- n8n (208k), Open WebUI (156k), Redis (77k), per GitHub on 2026-10-19. Stars measure attention, not fit; read the Catch.
- What is the catch with Redis?
- License: not MIT. Since Redis 8 the server is tri-licensed RSALv2 / SSPLv1 / AGPLv3 at your choice — AGPLv3 is the only OSI option and carries network copyleft; 7.4–7.x was RSALv2/SSPLv1 only.