Here's how to download and compile the sketch:
1. On the github page, press the green button "clone or download"
2. Open the downloaded file "bitX40-master.zip" and extract all files to a location of your choice
3. Go to the extracted folder "bitX40-master" and open it
4. Inside this folder there are several files. Find the file named "raduino_v1.27.7.ino" and double click it
5. The Arduino IDE will start
6. A message box will pop-up: The file "raduino_v1.27.7.ino" needs to be in a sketch folder named "raduino_v1.27.7". Create this folder, move the file, and continue?. Click YES.
7. The downloaded sketch will now be opened and shown in your IDE.
8. In the IDE, go to Sketch => Verify/Compile (or press ctrl-R), then the sketch should be compiled without errors.
73 Allard PE1NWL