FYI This sounds a bit like the 'standard error' that you get with a lot of non-app store programs on Mac nowadays. It's usually solved by moving the app from the folder you downloaded it to — e.g. move it to Applications — and then running again. Also, due to permissions/security, you might need to open it via right-click (menu), then "Open".
If you do all of that, you might then be faced with the "quit unexpectedly" message ... or you might get lucky :)