Installing software from an unidentified developer
Every time I try to install my plug-in I get an error telling me the developer is not identified. How do I install my plug-ins?
Mac OS X versions 10.8 and newer have a security feature that may display this message when trying to install older software. All of our current plug-ins are updated for this security feature, so they should not cause a problem.
This feature is designed so that you don't accidentally install software from a malicious site. While this is normally a good thing, it can get in the way of valid programs from time to time. Thankfully, turning it off is quite simple.
Start by opening your System Preferences and clicking the Security & Privacy option.
Once you are on the Security & Privacy options, you will see a heading titled "Allow applications downloaded from:". If this section is grayed out, you will need to click your lock in the lower corner and enter your computers password.
Once it is unlocked, just select "Anywhere" from the list options. You can secure your system again by selecting the "Mac App Store and identified developers" option.
macOS 10.12 Update
"Anywhere" option has been removed starting with macOS 10.12. You can allow the program to run by clicking the “Open Anyway” button in the General pane of Security & Privacy preferences. This button is available for about an hour after you try to open a program.
If you don't see the option try running the program again. When the "Unidentified Developer" message shows, click OK. Open System Preferences and select Security & Privacy. The General section will now show the "Open Anyway" option. Click it and the program will run.