The page you requested is no longer the latest version of the gist ontology. We switched to using the w3id.org/semanticarts namespace starting with gist version 12.
The latest version can be found at:
https://w3id.org/semanticarts/ontology/gistCore
(rdf-xml)
https://w3id.org/semanticarts/ontology/gistCore.ttl
(Turtle)