I tried to launch The Witcher 2 but I get a d-bus error after pressing launch game on the launch screen.
vurdaan@MSI-Tumbleweed:~/GOG Games/The Witcher 2 Assassins Of Kings Enhanced Edition> ./start.sh
Running The Witcher 2: Assassins Of Kings - Enhanced Edition
** Message: window size should be 487x713
vurdaan@MSI-Tumbleweed:~/GOG Games/The Witcher 2 Assassins Of Kings Enhanced Edition> dbus[12592]: arguments to dbus_message_new_method_call() were incorrect, assertion "path != NULL" failed in file dbus-message.c line 1362.
This is normally a bug in some application using the D-Bus library.
D-Bus not built with -rdynamic so unable to print a backtrace
./saferun.sh: line 21: 12592 Aborted (core dumped) "${EXEC}" "$@"
I think it will be hard to help based on the message alone. I guess one would have to examine the core that was dumped to find out what is wrong. Maybe try to contact GOG on this?
I had the same error, and I was able to launch the game using using some steam libraries. Once steam is installed, run the following command in the directory containing the executable.