---
title: "Open source and hosted Arete"
description: "What is open source in Arete and under which licences, and what the hosted service adds, including cloud dev environments."
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> For the complete documentation index optimized for AI agents, see [llms.txt](https://docs.arete.run/llms.txt) or [llms-full.txt](https://docs.arete.run/llms-full.txt). A markdown version of this page is available at [/getting-started/open-source-and-hosted.md](https://docs.arete.run/getting-started/open-source-and-hosted.md) or by sending `Accept: text/markdown`.
Arete's client SDKs, CLI, protocol authoring tools, and stack tooling are open
source. The hosted service at `api.arete.run` runs protocol deployments and
cloud dev environments and adds registry discovery, review, receipts, and
managed live data. This page explains those boundaries.

## What is open source

The SDKs, the CLI and the tooling you install into a project are in the
[AreteA4/arete](https://github.com/AreteA4/arete) repository:

| Component                                                       | Licence    |
| --------------------------------------------------------------- | ---------- |
| The `a4` CLI, its dev UI and the MCP server (`a4 mcp`)          | Apache-2.0 |
| The stack DSL, the interpreter and the server crates            | Apache-2.0 |
| The hash formats (`arete-hash`)                                 | Apache-2.0 |
| The Rust SDK and `arete-idl`                                    | MIT        |
| The TypeScript SDK (`@usearete/sdk`) and React bindings         | MIT        |
| `@usearete/protocol`: authoring, contracts, and handler tooling | MIT        |
| The Python SDK (`arete-sdk`)                                    | MIT        |

Each package's `LICENSE` file is authoritative. Self-hosting the
[open-source stack server](/a4-server/overview/) for your own app is welcome.
That server provides live projections and typed reads. It does not supply the
hosted protocol execution service or cloud dev environments. Installing the
open-source protocol authoring package does not install a self-hosted protocol
runtime.

## Development: cloud dev environments

[`a4 dev`](/cli/local-development/) develops against an Arete cloud dev
environment: a persistent fork of mainnet that Arete hosts for your account,
where your protocol runs as it will in production, decoded by the same
decoder. The CLI, the MCP server, the dev UI and your keys stay on your
machine: transactions are signed locally, and `a4 dev up` serves the
environment's RPC on `127.0.0.1` for wallets and apps. Environments count
against your plan (environments, active hours, storage, requests).

## What the hosted service adds

| Hosted                    | What you get                                                                                                                                             |
| ------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Registry and discovery    | Packages that agents and MCP clients find by intent, with exact versions to install                                                                      |
| Review and receipts       | Reviewed releases, and a signed receipt for each attested execution that anyone can check offline and against the chain (`protocol_receipt` in `a4 mcp`) |
| Current program knowledge | Program specs kept current as programs upgrade                                                                                                           |
| Hosting                   | Live stacks with history, protocol deployments, and SLAs                                                                                                 |
| Cloud dev environments    | Persistent mainnet forks for development, with checkpoints, branches, rebase, scenarios and transaction previews                                         |

## Fees

Fees for hosted protocol execution support discovery, review, and operations.
Arete sets the fee; a deployment can name a wallet for the creator's share.
The execution summary and attested receipts show the applicable fees and
creator allocations.