The primary goal of Fedora CoreOS is to be useful directly, and to have users deploy containers for applications, etc.
Some people and organizations have asked about creating custom derivatives of Fedora CoreOS using this project. This is supported on a best-effort basis. Supporting these use cases is not a primary goal of coreos-assembler, though we try not to purposely break them. Also note that coreos-assembler is still evolving, and it’s likely that there will occasionally be breaking changes. You should subscribe to releases to make sure you’re aware of these. That said, we do try to maintain a stable interface between coreos-assembler and the “source config” repo.
Maintaining a custom operating system build is a nontrivial undertaking that you shouldn’t take lightly. But we will make efforts to document changes and keep coreos-assembler relatively stable.
coreos-assembler is used to build RHEL CoreOS, but coreos-assembler is not a Red Hat product at the current time.