Multi Otsu - Plug In Not working

Hi All - I am trying to get the 'multi-otsu" thresholding plug-in to work for my image segmentation. When I click the source file online it takes me to a java code which I am able to run by selecting file > new > script and copying and pasting the script into the console, then I press compile and run. However, I get an error that it cannot find the java.jar file.

When I look at the website the class is not available for download and I am not sure how to proceed. If anyone can help that would be fantastic. I am very new to coding.

Plug-in Webpage: Multi Otsu Threshold - ImageJ