To keep using the service, customers must upgrade to OS X Mountain Lion. Emails announcing the shutoff began reaching Lion users last week.
Apple introduced a beta of Messages for Lion in February alongside the surprise release of a developer preview of OS X Mountain Lion.
Mountain Lion includes Messages, as well as several other features and services that debuted on iOS, Apple’s mobile operating system that powers the iPhone and iPad.
Apple pulled the download of the Messages beta for Lion in mid-June, when at its annual developers conference company executives revealed more information about Mountain Lion, including its price and a July ship date. Lion users, however, could still run Messages if they had already installed the beta.
But Messages’ future is under a patent cloud: Last Tuesday, VirnetX both won a $368 million jury verdict against Apple in a patent infringement case and filed a follow-up lawsuit alleging violations by new Apple products, including Mountain Lion.
The case that was decided last week and the new suit both cited FaceTime and Messages, Apple’s video chat application and SMS text-replacement, respectively, as infringing four VirnetX patents.
According to Web metrics company Net Applications, OS X Mountain Lion has grabbed approximately 26 percent of the Mac operating system usage base since its July roll-out.
