On the livestream I detailed this a bit. Angeldust has a single "domain model" containing all item, entity and object properties contained in a PHP code generator that generates C++ source code and header files for use in the client, server and asset tools. It also generates PHP files for use in the interactive and tied-to-the-game website. The website is also in PHP.

The client uses Objective-C to integrate certain platform features into the C++ codebase on iOS and macOS. Java is used for some functionality not provided by the Android NDK.

Seems like the other languages were for the frontends. C++ core, Java for Android, objC for iOS, php for web