I'm trying to run ERA for Mac. I've tried the latest versions (both the one listed in this thread and the latest one available on DriveThruRPG). They both fail with the message "“ERA.app” is damaged and can’t be opened". Note that this is not a 64-bit issue (the ERA-Server is listed as "Mach-O 64-bit executable x86_64", and I get the failure on both 10.15.7 and 10.13.6).
When I try to verify the program's Gatekeeper status, it complains "ERA.app: invalid Info.plist (plist or signature have been modified)".
Have you already tried the steps mentioned in the Installation Instructions? Just in case they are pasted below:
In macOS (for macOS Sierra 10.12 and higher): Extract the files in the downloaded ERA-Mac zip file.
Execute the application "ERA-RMC.app" or "ERA-RMFRP.app" depending on your ruleset. Installed books, characters and adventures are stored separately for each of the rulesets.
In macOS 10.15 Catalina and higher, you might need to open a terminal and execute the following command to allow ERA as a registered application:
sudo xattr -d com.apple.quarantine [LOCATION OF ERA.app]
sudo xattr -d com.apple.quarantine [LOCATION OF ERA-RMC.app]
sudo xattr -d com.apple.quarantine [LOCATION OF ERA-RMFRP.app]
For example:
sudo xattr -d com.apple.quarantine Downloads/ERA-Mac/ERA.app
sudo xattr -d com.apple.quarantine Downloads/ERA-Mac/ERA-RMC.app
sudo xattr -d com.apple.quarantine Downloads/ERA-Mac/ERA-RMFRP.app