https://schema.org/docs/developers.html offers http and https variants of the ontology (though in #2852 I question whether that's a great idea):

• https://schema.org/version/latest/schemaorg-current-http.jsonld
• https://schema.org/version/latest/schemaorg-current-https.jsonld

However, requesting just the JSONLD context (see #2851) doesn't make that distinction.
Both of these

curl -I -L -Haccept:application/ld+json http://schema.org/
curl -I -L -Haccept:application/ld+json https://schema.org/

return the same link:

link: </docs/jsonldcontext.jsonld>; rel="alternate"; type="application/ld+json"

No matter whether you access it by http or https

• http://schema.org/docs/jsonldcontext.jsonld
• https://schema.org/docs/jsonldcontext.jsonld

It returns the same file, which defines ontology terms as http:

        "schema": "http://schema.org/",