Licensing

The runtime: Apache-2.0

The Seshat runtime is published under the Apache License 2.0. The repository is seshat-runtime, copyright 2025-2026 KPO-Tech. You can use it, change it, redistribute it and build a commercial product on it, as the licence says.

This covers the engine and everything you reach through the SDK (pkg/), the gRPC server and the other packages, with the exception described next.

The terminal interface has another origin

The terminal interface, in tui/internal/seshattui, was built from the terminal interface of Crush by Charmbracelet, Inc. Crush is published under the Functional Source License 1.1, MIT Future License (FSL-1.1-MIT):

• The terminal command and its interface are the tui module, apart from the engine: the engine (pkg/, cmd/grpc, the rest of internal/) does not contain or import that code, and a test fails if it starts to.
• You may use, copy, modify and redistribute it for any purpose except a Competing Use. The licence defines a Competing Use as making the software available to others in a commercial product or service that substitutes for Crush, or for another product or service of Charmbracelet that uses it.
• Each version of Crush becomes available under the MIT licence two years after it was published.

What it means for the Seshat repository:

• The files of tui/internal/seshattui that come from Crush stay subject to the FSL-1.1-MIT in addition to the Apache-2.0 terms of the rest of the repository. Apache-2.0 does not replace it for them.
• Which files are copied and which were written for Seshat is not recorded file by file. Until it is, the whole directory is treated as subject to the Crush licence.
• The engine does not use that code.

In practice:

You want to	What it means
Run seshat, use the SDK or the gRPC server, in your company or your product	Nothing special. The Apache-2.0 terms apply to what you use
Redistribute the terminal interface inside a commercial coding-agent product	Read the Crush licence first, or leave tui/internal/seshattui out and use the engine through the SDK or gRPC

The authoritative statement is the NOTICE file of the repository, and docs/licensing.md explains it.

SeshatOS and SeshatCloud

SeshatOS and SeshatCloud are source-available, not open source: the code can be read, and you can use and host it yourself, but the licence limits resale. Only the runtime is open source.

The page Open source and licenses compares the three on the website.