Apple's released a number of different developer preview builds of OS X Mountain Lion in preparation for its release, and things took a huge step forward today: according to 9to5Mac, Apple has pushed the first Golden Master build out to developers. This doesn't mean the retail release is necessarily imminent, however; developers will still be looking to see if there are any show-stopping bugs, and Apple hasn't been shy about releasing multiple Golden Master builds before. Still, it's a sign that things are on track for the operating system to make its official debut later this month for $19.99.