You're requesting insecure (i.e. non-HTTPS) content from within a HTTPS page - try accessing the page over standard HTTP and you'll probably find it works.
CTRL+SHIFT+J or choose from the
Tools menu). You'll see an error like this:
[blocked] The page at https://lemanrus.pythonanywhere.com/maps ran insecure content from http://www.openlayers.org/api/OpenLayers.js.
Uncaught ReferenceError: OpenLayers is not defined maps:16
Presumably it works in other browsers because they have slightly different security policies.