Open Source AI Agent Tools
The 18 tools in our index with a clean, unrestricted OSI-style license (MIT, Apache-2.0, GPL-3.0-or-later or AGPLv3) — free to fork, self-host and run forever, no source-available caveats and no proprietary layer gating the part you would actually run.
We checked the license behind all 64 tools in our index and found 23 that call themselves open source in some form — but only 18 clear the bar of a clean, unrestricted license with no strings attached. This collection is those 18: the tools you can fork today, self-host forever, and keep running even if the vendor disappears, with nothing held back behind a separate commercial tier.
The other five "open" tools don't make this list, and that's deliberate: n8n and Dify both hedge their openness with a license condition their own docs tell you to check (fair-code, added-conditions Apache), Mastra and OpenHands are open at the core but gate their enterprise controls behind a separate paid license, and Warp open-sourced only its terminal client (AGPL-3.0/MIT) — Oz, the cloud-agent platform that actually runs and coordinates its agents, stays closed-source. Real, legitimate business models — just not a "no caveats" self-hosting story. See our full license census for the complete breakdown, caveats included.
Why this collection
A tool earns a place here only if its entire self-hostable codebase carries a clean, unrestricted OSI-style license — MIT, Apache-2.0, GPL-3.0-or-later, or AGPLv3 — with no source-available carve-out, no fair-code condition, and no proprietary enterprise layer gating the part you'd actually run. Verified against each tool's own GitHub license file or our sourced listing research, not a vendor's marketing claim of "open source."
- LangChain
The most widely-used framework for building LLM apps and agents, with LangGraph for stateful control.
The most widely adopted agent framework; MIT-licensed core, free to self-host with no vendor lock-in.
- CrewAI
A popular open-source Python framework for role-based, collaborating multi-agent teams, free to self-host, now a stable 1.0 release with an optional managed AMP cloud layer.
MIT-licensed multi-agent orchestration framework, reached a stable 1.0 general-availability release in October 2025.
- Microsoft AutoGen
Microsoft’s open-source framework for orchestrating conversations between multiple AI agents.
Microsoft's MIT-licensed multi-agent framework — free to self-host, pay only your own model provider.
- Microsoft Agent Framework
Microsoft’s production-ready, open-source successor to AutoGen and Semantic Kernel — one agent SDK for .NET, Python and Go.
Microsoft's MIT-licensed successor to AutoGen and Semantic Kernel — free to self-host across .NET, Python and Go, or an optional Azure-billed managed layer on top.
- LlamaIndex
The data framework for LLM apps, RAG-first, now with agent workflows and a document-parsing cloud.
MIT-licensed core framework for building agents over your own data; the paid LlamaCloud parsing layer is optional.
- OpenAI Agents SDK
OpenAI’s lightweight open-source framework for building agents, handoffs, guardrails and tracing in a few primitives.
MIT-licensed and free to self-host — OpenAI's own lightweight SDK for building agentic workflows.
- Pydantic AI
The type-safe agent framework from the Pydantic team, that FastAPI feeling for building AI agents.
MIT-licensed, type-safe Python framework from the team behind Pydantic — free to run anywhere.
- Letta
A stateful-agent framework — open-source, memory-first agents whose context, tools and identity persist as a durable server object instead of resetting between sessions.
Apache-2.0 licensed agent framework with persistent memory; self-host free or opt into managed Letta Cloud later.
- Cline
The open-source coding agent, an autonomous, bring-your-own-key agent that lives in your editor, terminal or SDK.
Apache-2.0 licensed VS Code, JetBrains and CLI agent — only Enterprise SSO and support sit behind a paid tier.
- Aider
AI pair programming in your terminal, an open-source CLI agent that edits your code and commits to git.
Apache-2.0 licensed terminal coding agent, free forever — bring your own model API key or run a local model.
- OpenAI Codex CLI
OpenAI's open-source (Apache-2.0) terminal coding agent, bundled into ChatGPT plans from Free through Pro — Business seats are now grandfathered-only.
Apache-2.0 licensed CLI is fully open, even though the OpenAI models it calls are not.
- OpenCode
A free, open-source (MIT) AI coding agent for the terminal, desktop and IDE, bring any of 75+ model providers, including your own local Ollama models.
MIT-licensed terminal coding agent with 188,976 GitHub stars — one of the most active open-source projects in the category.
- Zot
A free, MIT-licensed coding-agent harness in one Go binary, branch any session from any past message and view it as a tree, plus a Telegram bridge.
MIT-licensed single Go binary, no signup or Docker required — bring your own API key or run local Ollama models.
- Juggler
An open-source, GUI-based workbench for AI coding agents, branching session trees, not a linear transcript. Free, AGPLv3, by JUCE creator Julian Storer.
AGPLv3 for the main app, Apache-2.0 for its extension SDK — a stronger copyleft commitment than most rivals.
- LiveKit Agents
The open-source, self-hostable voice agent framework, Apache 2.0, provider-agnostic, and the infrastructure behind ChatGPT’s Advanced Voice Mode.
Apache-2.0 licensed voice-agent framework — the one clean open-source pick in an otherwise all-proprietary voice-agents category.
- GPT Researcher
An open-source autonomous research agent that plans, searches many sources and writes a cited report.
Apache-2.0 licensed — the only clean open-source pick in the research-agents category.
- Zed
The open-source, GPU-native code editor built from scratch by Atom's creators — runs Claude Code, Codex and other agents via the open Agent Client Protocol it created. Free forever; Pro from $10/month.
GPL-3.0-or-later core (Apache-2.0 for select components) — the first full IDE in this collection, rather than a CLI tool or editor extension.
- Google Agent Development Kit
Google's open-source, code-first agent SDK — four language runtimes, native A2A + MCP protocol support, and an optional managed Agent Runtime on Google Cloud.
Apache-2.0 licensed across all four of its language SDKs (Python, Go, Java, TypeScript) — Google's own official agent framework, free to self-host anywhere.