One of the most common questions asked of Mac 911 is, “How do I merge or transfer purchases from one Apple ID/Account to another?” The answer for over 20 years has been the same: You can’t. Until now.
Way back in the mists of time–the year 2000–Apple created iTools, its first cloud-hosted service, about six years before “cloud computing” even existed as a term. As part of iTools, you registered an account name paired with an @mac.com address. iTools later morphed into .Mac (2002) and MobileMe (2008, @me.com) before settling into iCloud (2011, @icloud.com).
Read more at Macworld.com