That probably is the reason. I'm using rpg maker 2003 for this, which I believe is initially only Windows compatible.
I did replace the .exe file with one that should hopefully be mac compatible in the newest update. The new .exe did change the graphics options to be accessible with F1 and the characters positions on the battle screen are unfortunately shifted, but everything should be the same otherwise.
The new .exe has a green icon next to it. Let me know if this one works for your system!