this code has moved to https://github.com/openapi-processor/openapi-processor-base/tree/main/openapi-processor-core
this is the re-usable core of the openapi-processors that generate java code.
It reads the OpenAPI yaml, converts it to an internal model and provides writers to generate java code.
See here.
to use snapshot versions add https://oss.sonatype.org/content/repositories/snapshots as maven repository to your build file.