I've updated the game with a new Mac build, please check it out and see if it works for you! It should be runnable either just so, or with cmd-click>Open, or maybe through Itch.io desktop app which usually helps with Mac games a lot.
Otherwise if this fails, please search for g_debug.txt or c_debug.txt files which are created temporarily somewhere in the game's directory when trying to run it.
Also you may try downloading the RPG file format player for Mac from the engine's website and running to open the .rpg file of the game:
https://hamsterrepublic.com/dl/ohrrpgce-mac-minimal-x86_64.tar.gz
Please let me know if you succeed with any of this!