Some code systems in the FHIR Specification, such as language tags, don’t display. Why is this the case?
There are a number of instances in the FHIR specification where CodeSystems are not displayed in the spec. This falls into two main reasons:
1. The code system is too large for the publication tooling to handle. I think the full language code system falls into this category 2. The code system us Intellectual Property of another organization. This prevents HL7 from publishing a specification that incorporates the IP of another body. There is a note about this in the CARIN Blue Button IG: http://hl7.org/fhir/us/carin-bb/STU1/Terminology_Licensure.html
Onyx is evaluating how licensed code systems are incorporated into OnyxOs. Some of that may depend on how a client is implementing OnyxOs. It can quickly become a complex issue.