With the consistent iOS-ifying of Mac OS X, and the introduction of Apple’s Mac App Store last year modeling the iOS App Store’s Apple-controlled distribution platform, some have questioned whether OS X will soon resemble the iOS ecosystem. That is, will Apple attempt to mirror the so-called “walled garden” approach of the App Store by requiring users to only run software specifically approved by Apple for use on Macs?

The good news is Apple’s OS X 10.8 Mountain Lion developer preview does not impose that restriction. Instead, Apple introduced “Gatekeeper,” a new system for developers to sign their apps, and a new method within System Preferences for users to better control which apps have access to their Mac. While claiming malware is “hardly an issue on a Mac,” Apple said Gatekeeper would improve security and help users avoid malicious software. By default, the feature only allows apps from the Mac App Store or those singed by identified Apple developers…

Apple’s website that describes Gatekeeper starts with some advice: “The safest place to find apps for your Mac is the Mac App Store.” However, Gatekeeper also allows devs to sign their non-Mac App Store apps with a unique Apple Developer ID. From an end-user’s perspective, Gatekeeper is essentially an evolution of File Quarantine that prompts a user to confirm the first time a file downloaded from the Internet is ran.

For users in Mountain Lion, there are three new options (pictured above) presented in the Security & Privacy pane of System Preferences. Under General, there is now the ability to “Allow applications downloaded from:” with the following three options: “Mac App Store,” “Mac App Store and identified developers,” and “Anywhere.” Even though the “Anywhere” option allows users to download anything just like they could in past versions of OS X, many are quick to point out the removal of the feature in the future would leave OS X incapable of running non-Apple approved third-party apps. Apple does offer an option to easily override Gatekeeper when installing an app by Control-clicking.

MacWorld explained Apple could revoke a developer’s license if its found distributing malware in Mountain Lion, and Gatekeeper will update a blacklist of those developers daily. Gatekeeper will apparently prevent software from developers on the list from running in Mountain Lion: