Hey guys, I’m in the process of downloading the Despecialized Edition, and I’ve encountered a small problem early on…

I’m following this guide: https://docs.google.com/document/d/1yLsvexWBVM8IYSGopKuSfsGk5YIgCwQWd23bqb5ryD4/pub#h.y4gpzrxunb9c

And I’m up to section 4, step 4. When I attempt to open the file ‘frd.jar’ a pop up says “frd.jar is damaged and cannot be opened” bearing in mind I’m using a Mac.

So does anyone know how I can repair the file or otherwise fix this issue?
Any help would be appreciated. Cheers.