Which AI Agent Tools Are Actually Open Source? A License Census

“Open source” shows up in the marketing copy of a surprising number of AI agent products that are, on closer reading, a proprietary SaaS product with a free tier. It’s also true in the other direction: some genuinely open, self-hostable frameworks barely say the word at all. Since license terms decide whether you can fork, self-host, resell, or simply keep running a tool if the vendor shuts down or gets acquired, we went through every one of the 49 tools in our index and pulled the actual license — not the vendor’s adjective for it.

The headline count

19 of 49 tools (39%) are open source in some form. But “open source” isn’t one thing, and the gap between a clean permissive license and a marketing claim matters if you’re deciding what to build on:

• 15 tools carry a clean, unrestricted OSI-style license (MIT, Apache-2.0, or AGPLv3) across their entire codebase, free to self-host with no carve-outs: LangChain, Microsoft AutoGen, LlamaIndex, OpenAI Agents SDK, Pydantic AI, CrewAI (all MIT); Cline, Aider, OpenAI Codex CLI, LiveKit Agents, Letta, GPT Researcher (all Apache-2.0); OpenCode, Zot (both MIT); and Juggler (AGPLv3 core app, Apache-2.0 extension SDK).
• 2 tools ship an open core with a separately-licensed Enterprise layer: Mastra is clean Apache-2.0 at its core but gates its Enterprise controls (RBAC, SSO, IAM) behind a separate source-available license; OpenHands is MIT everywhere except its enterprise/ directory, which carries the PolyForm Free Trial License 1.0.0 instead. In both cases the part you’d actually self-host is fully open — the enterprise layer on top isn’t.
• 2 tools call themselves open source with a real license caveat: n8n is “fair-code,” a source-available license that is explicitly not OSI-approved open source — n8n’s own cons admit “check terms for commercial resale.” Dify ships an “Apache-2.0-derived” license with added conditions our sourced research flags as “not pure OSS.”
• The other 30 (61%) are closed-source products — no code to inspect, no self-hosting option, and your only continuity guarantee is the vendor staying in business (a real question — see our AI agent acquisition wave field guide).

The category split is the real finding

Open-source rate is not evenly spread — it tracks almost exactly with who the buyer is:

Category	Open source	Share
Agent frameworks	8 of 8	100%
Coding agents	7 of 15	47%
Agent platforms	2 of 5	40%
Research agents	1 of 5	20%
Voice agents	1 of 6	17%
Sales & marketing agents	0 of 5	0%
Support agents	0 of 6	0%

Every framework in our index is open source — no exceptions. That’s not a coincidence: a framework’s entire value proposition is code you import and run yourself, so a closed-source framework would be a contradiction in terms. Coding agents are the most genuinely split category, roughly half proprietary IDE/SaaS products (Cursor, GitHub Copilot, Devin, Replit Agent, Bolt.new, Windsurf, Factory) and half open, self-hostable CLI tools (Cline, Aider, Codex CLI, OpenCode, Zot, OpenHands, Juggler).

Agent platforms is the category worth reading twice. Both of its “open source” entries — n8n and Dify — are the exact two caveated cases above. Zero platforms in our index ship a clean, unrestricted open-source license; the two that claim openness both hedge it with license conditions their own docs tell buyers to check. If license-clean self-hosting is a hard requirement for an orchestration platform, neither of the two nominally-open options in this category clears that bar without reading the fine print first.

Sales/marketing and support agents are 0% open source across every listing we track. These are the categories closest to being sold as a finished business outcome (leads booked, tickets resolved) rather than infrastructure a team assembles — and that shows up directly in the license column: buyers here are choosing a vendor relationship, full stop, with no self-hosted fallback if that relationship ends.

The full table

Tool	Category	Open source?	License / note
LangChain	Agent frameworks	Yes	MIT
CrewAI	Agent frameworks	Yes	MIT
Microsoft AutoGen	Agent frameworks	Yes	MIT
LlamaIndex	Agent frameworks	Yes	MIT
OpenAI Agents SDK	Agent frameworks	Yes	MIT
Pydantic AI	Agent frameworks	Yes	MIT
Mastra	Agent frameworks	Yes	Apache-2.0 core; Enterprise controls are a separate source-available add-on
Letta	Agent frameworks	Yes	Apache-2.0
Cline	Coding agents	Yes	Apache-2.0
Aider	Coding agents	Yes	Apache-2.0
OpenAI Codex CLI	Coding agents	Yes	Apache-2.0 (CLI is open; the models it calls aren’t)
OpenCode	Coding agents	Yes	MIT
Zot	Coding agents	Yes	MIT
OpenHands	Coding agents	Yes	MIT core; enterprise/ directory is a separate PolyForm Free Trial source-available add-on
Juggler	Coding agents	Yes	AGPLv3 (app) / Apache-2.0 (extension SDK)
Cursor	Coding agents	No	Closed-source VS Code fork
GitHub Copilot	Coding agents	No	Proprietary
Claude Code	Coding agents	No	Proprietary
Devin	Coding agents	No	Proprietary
Windsurf	Coding agents	No	Proprietary
Replit Agent	Coding agents	No	Proprietary
Bolt.new	Coding agents	No	Proprietary
Factory	Coding agents	No	Proprietary
n8n	Agent platforms	Yes*	Fair-code (source-available) — not OSI-approved open source
Dify	Agent platforms	Yes*	Apache-2.0-derived with added conditions — not pure OSS
Lindy	Agent platforms	No	Proprietary
Relevance AI	Agent platforms	No	Proprietary
Sierra	Agent platforms, Support agents	No	Proprietary
GPT Researcher	Research agents	Yes	Apache-2.0
Perplexity	Research agents	No	Proprietary
Manus	Research agents	No	Proprietary
Elicit	Research agents	No	Proprietary
GC AI	Research agents	No	Proprietary
LiveKit Agents	Voice agents	Yes	Apache-2.0
Vapi	Voice agents	No	Proprietary
Retell AI	Voice agents	No	Proprietary
Bland AI	Voice agents	No	Proprietary
ElevenLabs Conversational AI	Voice agents	No	Proprietary
PolyAI	Voice agents	No	Proprietary
Clay	Sales & marketing agents	No	Proprietary
11x	Sales & marketing agents	No	Proprietary
Artisan	Sales & marketing agents	No	Proprietary
Qualified	Sales & marketing agents	No	Proprietary
Rox	Sales & marketing agents	No	Proprietary
Decagon	Support agents	No	Proprietary
Crescendo	Support agents	No	Proprietary
Cresta	Support agents	No	Proprietary
Intercom Fin	Support agents	No	Proprietary
Ada	Support agents	No	Proprietary

* n8n and Dify both describe themselves as open source; we’ve flagged both because their own materials name a specific condition (fair-code licensing terms; added-conditions Apache derivative) that stops short of an OSI-approved license. Read the row’s note, not just the Yes/No column, before assuming either behaves like MIT or Apache-2.0 in practice.

Why the caveats matter more than the yes/no column

A “no” in the table above is unambiguous — you’re a customer of a company, and your continuity depends on that company. The “yes” rows are where the real due diligence sits, because open source isn’t one guarantee:

• Clean OSI license (MIT/Apache/AGPL): you can fork it today, run it forever, and nothing the vendor does to their business changes that. This is the strongest continuity position in the table.
• Source-available / fair-code (n8n) or added-conditions (Dify): you can read the code and usually self-host it free, but commercial resale, hosting-as-a-service, or certain enterprise use cases may be restricted — the vendor has retained rights an MIT or Apache license would give away. Check the actual license text before you build a commercial offering on top.
• Open core with a proprietary layer (Mastra, OpenHands): the part you’d actually run is open, but the enterprise controls (SSO, RBAC, hosted multi-tenant deployment) sit behind a separate paid or source-available tier — a normal, disclosed pattern, not a bait-and-switch, but worth knowing going in.

None of this is a knock on any single vendor — fair-code and open-core are legitimate, common business models, not deception. The point is that “open source” on a landing page answers a marketing question, and the license file answers the buying question. They’re not always the same answer.

Methodology

Every row above is read directly from the sourced, gate-passed research already published on each listing — the same openSource field and license language every listing cites with a primary source (usually the tool’s own GitHub repository, pricing page, or licensing docs). This is not a new survey and nothing here is estimated: a tool is marked open source only when its own listing states it with a citation, and the license name is quoted from that same sourced text — where our sourced research doesn’t yet name a specific license, we say so rather than filling the gap with an assumption (CrewAI’s MIT license and OpenHands’ enterprise/-directory license split, both confirmed directly against the respective GitHub LICENSE files, were added to their listings after this article’s first publication and are reflected in the table and headline bullets above). Category percentages are computed from the current Published corpus (49 listings across 7 categories, with Sierra counted in both categories it belongs to) and will shift as we add and re-verify listings — this is a snapshot of 2026-07-24, not an index on the update schedule our State of AI Agents 2026 report follows.

For the general vendor-lock-in angle beyond licensing — ownership, funding, and acquisition risk — see our AI agent acquisition wave field guide. For a narrower, deeper cut on six terminal coding agents specifically (license and model portability), see Terminal AI coding agents: open, portable, or locked in?. The Open Source Initiative’s license list is the reference we used to determine which licenses in this table are OSI-approved.