Installation on the Mac, “InstallVensim” can’t be opened because Apple cannot check it for malicious software.

The latest versions of Vensim are fully digitally signed and notarized by Apple, so if you are seeing this, it suggests their service is down, or some other issue with your computer.

The workaround is to download the installer, then right-click to open. You still get the warning message, but the should now still open and install.