I’ve added my Denon DN-2000F interface code to SourceForge:
https://sourceforge.net/projects/denon-dn-interface/
The interface is in the form of a DLL/shared library which exposes functions and callbacks.
At the moment, only Windows is supported. Linux and macOS will follow shortly.
There’s a .NET demo app which shows the interface in action, and it allows you to use both decks on the RC-35B to control the playback of an audio file. The .NET app uses the amazing Un4seen BASS Audio Library for the playback.
See it in action: https://youtu.be/nZoMyLBqc3w
Documentation to follow!