So based on some research, it sounds like MacOS Catalina introduced some new security features for applications that aren't on the Apple Store which is why you're running into that.
I'm primarily a Windows user, so I wasn't aware of this update until now; sorry about that! I'll get working on a fix, and hopefully get it out this week.
In the mean time, if you really want to play the game there does appear to be a work around... but you'll have to follow this guide:
Hi Bulbware! Sorry, this issue is taking longer to resolve because of my job and I also don't have immediate access to a Mac at the moment. In the meantime, I can send you a Steam key; Steam should get around this issue entirely because it's trusted by Apple.
Is there an e-mail address I can use to send you the Steam key? Or social media I can DM you on?
hi lum! I just download PARANOIHELL and like others can't run it on MacOs Catalina. Could you please send me a Steam Key? Do you need the Paypal invoice in order to do so? You can email me: paolo.tedeschi@me.com
Ugh, sorry you're also running into the same issue! I'm currently in the middle of requesting a batch of Steam keys, so I should have some available in the next day or two.
When they're ready you'll be able to claim a key on the itch.io page 馃槉
