Whereas the Mac App Store provides an iOS-style curated app experience, current Mac owners are also able to install any application they desire from the web or elsewhere. As part of OS X 10.8 Mountain Lion, Apple will be introducing a third option: apps that are available outside the App Store, but are signed by digital certificates courtesy of Apple to help ensure they're malware-free. It's part of a new security feature called Gatekeeper, and Apple has officially started herding Mac developers in its direction. In an email sent out to today, Apple encouraged developers to begin signing their applications, plug-ins, and installer packages with their Apple Developer ID to take advantage of the feature (the Developer ID itself launched back in February).

Using Gatekeeper, Mac owners will be able to set their computers to install only App Store applications, App Store and Developer ID-signed applications, or any application whatsoever. It's unclear how users will take to Gatekeeper, and with Mountain Lion not scheduled to arrive until later this summer there's more than enough time for developers to get onboard. Apple is touting Gatekeeper as one of Mountain Lion's standout features, however, and with the company already encouraging developers to adopt the system, it's clear that Cupertino plans to put a lot of weight behind the feature.