I had great difficulty using the 16x2 GPIO LCD screen.
So as I finally found it, I post the problem here.
The line import RPi.GPIO as GPIO is missing at the top of the 'lcdchar.py' file.
Now things are much better, I continue to test Runeaudio, thank you for all your work.
Please try the public beta. With the latest update, there are settings for custom GPIO pins.