Apologies for not replying sooner, I have been experimenting on my computer and have figured out how to run the game (at least for me). My method is for Mac computers running 10.15 Catalina as the OS. I’m hoping this will also work for 11.0 Big Sur as well but no promises.
Step 1: download the latest Messy Academy Update mac.zip file to your desktop. At the time of this writing that is 0.13.5. When this file is downloaded it will appear as a folder on your desktop titled Messy Academy update 0.13.5 mac.
Step 2: Download the fix command file to your desktop. This will appear as a SHELL file titled Fix_Permissions.command
Step 3: Drag and drop the Fix_Permissions.command file into the Messy Academy update 0.13.5 mac folder. It should appear in the folder as a third item along with a credits.html file document and the game program Icon titled Acadamy_Reboot.
Step 4: Open the Terminal program on your mac located in the Applications folder.
Step 5: Now you need to execute on the SHELL file. With a terminal command window open enter: chmod u+x
Step 6: Now with both the Terminal window and the Messy Academy update 0.13.5 mac folder open side by side drag and drop the Fix_Permissions.command file into the terminal window just in front of the chmod u+x text. If done correctly the path to the file should appear so in general the complete command line should read chmod u+x /path/to/Fix_Permissions.command with the /path/to/ part varying depending on your mac’s file structure.
Step 7: Hit Enter in Terminal. Terminal should then execute on the SHELL file.
Step 8: Now click on the Academy_Reboot icon in the Messy Academy update 0.13.5 mac folder. The game should open just fine now.
A note on the previous instructions. One of the major areas of confusion is that on a mac the "tyranoscript.app" name for the game container file is hidden until the game actually opens and so saying “Place "Fix_Permissions.command" file in same folder as "tyranoscript.app"” does not help on a mac because you won’t know where to put it.
Hope this all helps someone in the future!