If you bought a new Mac anytime between June 11 and now, you’re entitled to a free copy of OS X 10.8—as long as you request it from Apple within 30 days.
June 11 was the first day of this year’s Worldwide Developers Conference, where Apple introduced its latest updates to the MacBook Air and MacBook Pro line. So, if you purchased any of those new machines after Apple’s announcement, you qualify for a free copy of Mountain Lion.
But it’s not only those people who own brand new machines who qualify. Anyone who bought any Apple computer—either directly from Apple or through an Apple Authorized Reseller—after June 11 also qualifies. That includes iMacs, Mac Pros, or even Mac Minis that have not been updated recently but are currently available from the Apple Store.
In order to obtain your free copy of OS X 10.8, you have to submit a request through Apple’sMountain Lion Up-to-Date page. After entering the details of where you bought your Mac and when, Apple asks for your contact information and your Mac’s serial number. Once you submit your claim and Apple verifies you in the system, Apple will send you a download code via e-mail where you can grab Mountain Lion from the App Store—no purchase required.