Open source
The code is public and the license allows you to use it, modify it and resell it. Only the Seshat runtime falls in this category (Apache-2.0).
One clarification: the Seshat terminal interface reuses code from Crush (Charmbracelet), published under the FSL-1.1-MIT license. That part remains subject to this license, which mainly forbids reselling it as a product competing with Crush.