Update 2: After a brief time online, Apple appears to have taken down the form to request a copy of Mountain Lion. You’ll still be able to request a copy at Apple’s original link following Mountain Lion’s official release.
Update: As noted by MacRumors, Apple’s form to request a free copy of Mountain Lion for new Mac owners is already live on the company’s website. After entering details about your purchase, personal details, and the serial numbers of your new Mac, Apple sends two emails —one with a password protected redemption code and another containing the password— to open it. The redemption code is not yet working in the Mac App Store.
Apple previously confirmed, when it unveiled the new Retina MacBook Pros and refreshed Mac lineups, that Mountain Lion would be available for free to those who purchased a Mac after June 11 through the Up-to-Date program. Since then, Apple has updated its website to confirm the free copy will be available to new Mac owners for 30 days from the release date, which will likely be sometime after tomorrow’s Q3 earnings call. Those who purchase a new Mac following Mountain Lion’s release will also have 30 days to claim their copy on Apple’s website.