The change will affect those who use their mac.com and me.com addresses as AIM IDs to log into iChat on older systems, as users running compatible versions of OS X Snow Leopard and OS X Lion can upgrade to OS X Mavericks for free.
Meanwhile, users running OS X Leopard are directed to purchase and upgrade to Snow Leopard and then install OS X Mavericks for free. If a user cannot upgrade to a newer version of OS X, then the creation of a new AIM ID on AOL's website will be required along with the need to repopulate a new contacts list.
iChat was discontinued in favor of Messages, which has been the default instant messaging application on the Mac since its first appearance in OS X 10.8 Mountain Lion. According to the latest data from Net Applications, Apple’s newest operating system, OS X Mavericks, holds a 51% share on all Macs, while the share of systems running older versions of OS X affected by this latest change is 19%.