When sending a POST request to the SPARQL endpoint, I get a nonsensical reply back:
MALFORMED QUERY: Lexical error at line 1, column 6. Encountered: "=" (61), after : "query"
Sending the same request with a GET request does work.
(Notice there a limitations to what can be done with a GET request, since the SPARQL query must be encoded in the request URL, resulting in very long URLs for longer queries.)