Apple on Monday released a "golden master" of OS X Mountain Lion to developers, putting the impending operating system on track to reach customers this month.
"Golden master," or GM, is a label some developers apply to software that is ready, or nearly ready, for shipping. Rival Microsoft calls the same milestone "release to manufacturing," or RTM, designating that the code is suitable for computer makers to install on new machines.
The appearance on the Apple developer website of Mountain Lion's golden master was reported Monday afternoon by several Apple-centric blogs, including 9to5Mac, and later confirmed by Computerworld.
Its debut means that the on-sale date for Mountain Lion is probably between two and three weeks away.
Last year, Apple issued the golden master of OS X Lion on July 1, then launched the operating system 19 days later on July 20. In 2009, the pause between OS X Snow Leopard's final version and its retail availability was somewhat shorter, 16 days.
The only official word from Apple thus far is that Mountain Lion will hit the Mac App Store, its sole distribution channel, this month. Based on the company's past practice, including last year's surprise announcement at an earnings call that Lion would launch the next day -- and with that quarterly call slated for July 24 this year -- Computerworld has pegged the most likely ship date as Wednesday, July 25.
Coincidentally, that would put the span between the final version's release and going on-sale at 16 days, the same number as for Snow Leopard.
Customers running Snow Leopard or Lion can upgrade to the new edition, which will be priced at $19.99, a 33% discount compared to 2011's Lion.
Users concerned about application compatibility can check the website RoaringApps, which lists the Mac programs that work with Mountain Lion's earlier builds, those that don't and the ones that balk in some way.
Applications that have been tested typically include users' comments that provide additional information on what worked and what didn't on Mountain Lion.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is email@example.com.
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