The application of JSON Schema to many of the JSON-like languages (CSON, JSON5, ...) may be obvious; however, I feel that JSON schema's utility for YAML is undersold.
Perhaps nothing will come of it, but I have created a
website for tracking JSON Schema's use against other languages similar to how
json-schema.org tracks implementations against JSON. Since it is encouraging the adoption of JSON Schema, I thought there might be interest here.
Right now the only interesting page is probably YAML. While I am the author of the linked implementation there, I was not the first, my extension superseded
this one which has more than 10k downloads.