Apple has told Mac owners running OS X Lion that the beta of Messages, its replacement for both the older iChat instant messaging service and SMS (short message service) texting, will expire Dec. 14.
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. The latter went on sale in July for $19.99, a third less than its two predecessors.
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% of the Mac operating system usage base since its July roll-out.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.