That's fuck up, they are running 6 years already and no one noticed this. Their source code is in github but no one knows if its fully open source or only partial.
Edit: I checked the website, OP is talking right with data request to
/getbalance.php in the
/app.js, but you can't read the actual code because it's been obfuscate and i checked the github repo and there's no
/getbalance.php file.
Here's the data request on
/getbalance.php