Unidentified developer

I'm getting a message from my mac saying "Your security preferences allow installation of only apps from the Mac App Store and identified developers". I have my mp3's info tag "open with" Qmidi Pro. I double click on the file & it opens. This has always worked until a couple of weeks ago. I look for Qmidi on Apple's App Store but can't find it. It has Mixage's MidiKit & MusicDeviceHost. Why is this?
I know I can change my security preferences to open apps from "Anywhere" but didn't want to do that unless it's the last option. Has something changed lately with Qmidi to make this happen?
Regards Tcmbruce

Trash all QMidi copies on your hd and download a signed one from this site.