I am under macOS Mojave and since the version 10.14.3 was published, I can not launch the game anymore. It crash instantly.
I did my little investigation and found out that in fact, the binary is compiled in PPC and i386 architecture. MacOS Mojave 10.14.3 (and later) is only compatible with x86_64 binaries.
In the future, to prevent people from having to compile the binaries themselves & install Xcode, could you compile OpenTTD into x86_64?
admin@MBP:/Applications/OpenTTD/.releases/1.8.0/OpenTTD.app/Contents/MacOS$ ./openttd -d 0.0.0.0
admin@MBP:/Applications/OpenTTD/.releases/1.8.0/OpenTTD.app/Contents/MacOS$ file openttd
openttd: Mach-O universal binary with 2 architectures: [i386:Mach-O executable i386] [ppc]
openttd (for architecture i386): Mach-O executable i386
openttd (for architecture ppc): Mach-O executable ppc