***** I have not verified that anyone with mac has actually managed to play this game 
with videos fully working by following the instructions below. 
If you have, I'd like to know. Thank you. ******

There are currently no releases for any other OS than Windows. 
You might still be able to play the game on any OS by running the jar file, 
providing you have java installed on your system with all the resources needed. 
However, javafx (needed for videos) is often not included in the typical java installation. 

You could try to make the game run properly by seeing to it that the JDK (java installation) 
used when you launch the game has javafx included. One such JDK is Liberica JDK which 
is the one used by the game and which can be downloaded here: 
https://bell-sw.com/pages/java-13/
Make sure you download the Regular version for your system, not the "lite". 
NOTE: If you do not download v13 from the link but instead download Liberica JDK 13.0.2+ 
you need the Full version. 
During the installation, keep the suggested features on the "Custom Setup" screen. 
This should make it your default JDK and it should solve the video problem.