MIT
Open source
The public agent layer is open source. It exists so agents, developers, and studios can inspect the bridge that connects AI tools to Summer Engine.
- CLI package
- MCP server
- Agent skills
- Hooks
- Plugin manifests
Source status
Summer's AI-agent layer is open source.
The desktop app is free proprietary software. The CLI, MCP server, skills, hooks, and plugin manifests are MIT open source. Hosted Summer AI, asset generation, storage, orchestration, multiplayer, and cloud services are paid.
Desktop
Free
The Summer Engine desktop app is free to download and use. You can make projects locally, use the editor, export games, and connect external agents through MCP.
- Desktop app
- Local editor workflows
- Local MCP setup
- External-agent workflows
- Project ownership
Hosted
Paid
Hosted Summer services are commercial because they run cloud models, storage, orchestration, and infrastructure that cost money every time they are used.
- Hosted Summer AI
- Asset generation
- Cloud storage
- Orchestration
- Managed multiplayer
Why this split exists
Open where auditability helps. Commercial where infrastructure costs money.
The agent layer is public because it is the part agents and developers need to inspect. It shows how the CLI installs Summer, how MCP exposes engine operations, and how skills teach agents game-development workflows.
The desktop app is free because creators should be able to build and export games without paying a platform toll. Its source is not public right now. That may change later, but the current public claim is not "the engine is open source."
Hosted Summer services are paid because they run expensive model calls and cloud systems. Paying for those services does not change who owns your game. You own your code, scenes, assets, and shipped build.
FAQ
Plain answers.
- Is Summer Engine open source?
- The AI-agent layer is MIT open source. That includes the CLI, MCP server, skills, hooks, and plugin manifests. The Summer Engine desktop app is free to download and use, but its source code is not public right now.
- Can I download the open repo and get the hosted Summer experience?
- No. The open repo is the agent layer. It helps agents connect to Summer Engine. Hosted Summer AI, asset generation, storage, multiplayer, orchestration, and cloud services are paid Summer services.
- 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.
- What do paid plans cover?
- Paid plans cover hosted Summer AI usage and cloud features that cost money to run, such as asset generation, storage, orchestration, and higher usage limits.
- Can I self-host the whole platform?
- No. The hosted AI brain, cloud orchestration, storage, billing, asset-generation backend, and multiplayer services are not open source or self-hostable today.
- Can I bring my own model key?
- For external agents, yes: use your agent's own subscription and connect through Summer MCP. Inside hosted Summer AI, bring-your-own-key is not available yet.
- Will the engine source be published later?
- Maybe, but not as the public claim today. If Summer publishes engine source later under a no-competing-engine license, the honest term would be source-available, not open source.
- What license applies today?
- The public AI-agent layer is MIT licensed. The desktop app is free proprietary software. Games and assets you create are yours, with no Summer royalties.