I somehow never got this program to work... so I created a simple command-line utility (using LibUSB) to just turn the display of this VR glasses on and then wrote a shader plugin for VLC to render normal videos in this weird side-by-side format required by those VR glasses. It's still experimental, but works okayish for me - if anyone wants to give it a try, it's on my repository under github.com/bauermaximilian/LG-360-VR-for-PC/
Edit: I just found out that this doesn't just work for watching movies, but since VLC supports using a (single) screen as video source (with source "screen://" and the additional options ":screen-fps=25.000000 :live-caching=0 :screen-left=1920"), this approach can even be used to display the whole desktop and applications like a web browser inside the VR glasses! It's a bit small though and doesn't display the mouse cursor.