Hi jezhawk.

I'm still running OS X 10.11.6 (my Mac doesn't support Sierra), but I was able to visit a retailer and perform limited testing on a display model running OS X 10.12.5 and can confirm your observations.

Unfortunately, I couldn't get past the "App is damaged… " message, even when applying the override solution (I suspect because admin privileges weren't available). I can offer some possible solutions, but I haven't been able to test them.

As of OS X 10.12, Apple requires users to authorize the use of any application not obtained from the Mac App Store or an identified developer. Apart from the removal of the "Anywhere" option, the official solution is identical to OS X 10.11 (override Gatekeeper).

When the "App is damaged…" message appears, click the "?" button. At the bottom of the help window, click the link to the override method and follow the instructions.

Some key points:
- your user account must have administrator privileges (the account you created when you set up your Mac will have these).
- locate the Riven Mac Installer using the Finder (do NOT use Launchpad).

Apart from that, control-click the app, then choose Open from the contextual menu.
If all goes well, you should get either a message advising that the app is from an unidentified developer or a request for your admin password (or both).

If you still can't open the installer (the "App is damaged…" message reappears), it's still possible to restore the "Anywhere" option to the Security settings, but hopefully that won't be necessary. I'll provide those details if required.