Same with https://freebitco.in/static/html/dplay_connect.html but notice the /static/ in these URLs.  They're just HTML pages that aren't being processed/built in some way by the server before delivery.

A 500 error would be most likely from code on the server used in generating the page running into an error.

For instance, if you try to access the homepage in a browser where you are not previously logged in, you'll get sent to the login screen. So, it's probably some issue with a database query that is tied to the user ID.  But who knows.