Yes I have verified that the JAR file is not signed so MacOS won't let it run without manually telling MacOS to run.
This means to run Minion on a Mac until someone fixes it, you will need to:
1) Download the Java (3.0.12) version of Minion here:
https://minion.mmoui.com/?download
2) Open the Minon3 folder it downloads in the Finder.
3) Right click (or ctrl-click) on the file "Minion-jfx.jar" and select "Open with..." from the menu.
4) Select "JavaLauncher" from the sub-menu.
5) A dialog will pop up that tells you it's unsigned and asks if you want to open it anyway. You agree to open it anyway.
Now Minion should launch and work fine.
Any time you want to run it in the future, simply right-click (or ctrl-click) on "Minion-jfx.jar" and select "Open" from the menu.
Hope this helps you and others who want to run Minion on the Mac.
Maybe the Minion devs will properly sign the app on Mac at some point.