BlueStitch42: I have found a patch that works flawlessly for me.
I realized that executing this (/Users/Shared/GOG.com/Galaxy/redists/GalaxyCommunication) every 5-15 seconds prevented the launcher from crashing. So I wrote a script that did it in the background for me !
All you have to do is create a new .sh file and run it using terminal, here's what you need to put in the file :
#!/bin/zsh
open "/Applications/GOG Galaxy.app"
while true; do
/Users/Shared/GOG.com/Galaxy/redists/GalaxyCommunication
sleep 2
done
Once created, open this .sh file with your terminal and it will open gog as usual, then execute the "fix" in the background every 2 seconds. it does open a terminal window that you can't close (otherwise the launcher crashes) but appart from that everything works fine.
You are a star! I had already given up. Yes, it works opening it every 5-10 seconds (lets me start the games). Wonderful!
I have no idea how to create the .sh file. But entering those lines in the terminal seemed to have the same effect.
I can now finally use GOG on my Mac. Thanks again!