Apple implemented application signing as a security measure with Mountain Lion. The default setting is to allow all Mac Store Apps and all apps from identified developers (signed apps). This is a reasonable setting that balances security and ease of use. And to be honest, I rarely encounter a problem but I occasionally want to install an unsigned app (that I trust). While I often see tips about how to enable this they all imply this change must be permanent. I loosen the settings, do the installation, and then restore the old setting. I’ve never had a problem doing this and I continue to be protected from unintended installations. So my process is:
1. Go to System Preferences -> Security & Privacy -> General tab and change the “Allow Applications…” setting to “Anywhere”.
2. Install the software
3. Return to system preferences and change the setting back to “Mac App Store and identified developers”
So for now, despite the wording, only app installs are blocked. The apps themselves still run once installed. At least for now.