I suppose that is a good tradeoff, like Red Hat providing RHEL source but not installation media. But it will make harder to get started with Chef, and I don't know if there is enough community motivation to create a CentOS equivalent for Chef. I hope AWS's Open Distro project takes on more software projects (https://opendistro.github.io/for-elasticsearch/).
IMHO this is already very hard to do. I tried recently and chef.io is an impenetrable labyrinth of different products, white sheets, data sheets, customer stories, and "Contact Sales" buttons.
Since everything Chef makes is used for production infrastructure, they have historically avoided doing anything that would break functionality for license compliance.
"All Chef’s software is mission critical and runs in a variety of different use cases and environments. As a result, we have not implemented hard enforcement and we don’t have any plans to change that. What we do have are commercial terms that we expect users of the software to honor. Users will have to accept the terms of the Chef End User License when they first run our software. Once the license acceptance has been acknowledged, acceptance can be automated to avoid the need for user input for further deployments. "