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Summer’s AI-agent layer is MIT open source. The Summer Engine desktop app is free to download and use, but its source code is not public right now. Hosted Summer AI, asset generation, storage, multiplayer, orchestration, and cloud services are paid Summer services.

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What is open today?

The public repo is the agent layer:
  • CLI
  • MCP server
  • Agent skills
  • Hooks
  • Plugin manifests
Repo: github.com/SummerEngine/summer-engine-agent

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What is free?

The Summer Engine desktop app is free to download and use. Local MCP workflows are free too, including workflows where you bring your existing Claude Code, Cursor, Codex, Gemini, Windsurf, or other agent subscription.

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What is paid?

Hosted Summer services are paid because they run cloud infrastructure and model calls:
  • Hosted Summer AI
  • Asset generation
  • Cloud storage
  • Orchestration
  • Managed multiplayer

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Is the engine app open source?

No. The desktop app is free proprietary software right now. If Summer publishes engine source later under a no-competing-engine license, the honest term would be source-available, not open source. For the public canonical page, see summerengine.com/source-status.