To get any data you have to specify a server.
Specifiy one by putting the name in a parameter called 'server'.

If your http accept request header includes application/json or a parameter named json is set the returned data is formatted as JSON, otherwise the data will be returned as a series of javascript variables simply because that was my original solution.

Regarding unavailable language, population, and type: On january 30th 2018 this informations was removed from the official server status page so it is unfortunatly no longer available. The variables remain for compatibility and in case the would ever return to the status page. Biorware's official post on this can be found here.