IBM is porting Lotus Sametime to Linux, the first time this enterprise instant messaging platform will support the popular open source operating system.

IBM will deliver a Linux version of the desktop client before mid-September in Sametime's version 7.5, which is now in beta testing, an IBM official said.

Meanwhile, the server piece will ship in the first half of next year, IBM's program director and senior product manager for real-time communication, David Marshak, said. IBM anticipates there will be client and server versions of Sametime for Linux operating systems from Red Hat and Novell.

IM is essential to communications in many workplaces, where IM systems have become communication hubs that provide, beyond text messaging, integration with telephony and email systems, business applications and Web conferencing.

IBM hasn't estimated what percentage of customers will deploy Sametime on Linux, Marshak said. However, interest is high in industries like education and government, and among small and medium-size companies, because of the generally lower costs of Linux systems and the flexibility of open source, he said.

"The two major themes are choice and cost of ownership," Marshak said.

Sametime's biggest competitor is Microsoft's Live Communications Server, which doesn't run on Linux. IBM and Microsoft have locked horns recently as they fight for enterprise IM customers.

The porting of Sametime to Linux is yet another swipe IBM is taking at Microsoft, research director with AMR Research, Jim Murphy, said. With this move, IBM offers a lower-cost operating system alternative for Sametime as many customers ponder whether to invest in Vista, Windows' upcoming upgrade, a likely more expensive and longer-term commitment, he said.

"There's a lot of competitive positioning in this move," Murphy said.

In June, IBM announced it was building links between Sametime and Microsoft's Outlook, Office and SharePoint applications. The links, slated for early next year, will give users access to Sametime 7.5 functionality from within those Microsoft products, an attempt to lure those users to the IBM system.

In January, IBM announced Sametime 7.5 will be linked with the public IM networks from AOL, Yahoo and Google, but it apparently couldn't reach an agreement with Microsoft over MSN Messenger. Marshak declined to comment on that issue, but the impasse apparently remains.

Other enhancements due in Sametime 7.5 include a refurbished user interface, improved privacy and security capabilities, embedded VoIP functionality and support for the Eclipse open-source application framework.

The Notes-Domino messaging and collaboration system, a sister product to Sametime, already runs on Linux.