Apple released a new open-source programming language, described as: Configuration that is Programmable, Scalable, and Safe.
It can translate the configuration to already existing configuration languages such as JSON, YAML, and others.
You can also embed those configuration files in some programming languages and produce code from them.
You can open source anything, really. This is just not useful in an ecosystem of Apple-only bullshit. Who cares if it’s open?