IBM is preparing a Linux version of Lotus Sametime for release in September. The company said that the Linux version of Sametime 7.5 would be the first open source version of the enterprise IM system.

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

The company 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, said Jim Murphy, research director with AMR Research.

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 Outlook, Office and SharePoint applications.

The links, pencilled in 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.

Other enhancements due in Sametime 7.5 include a refurbished user interface, improved privacy and security capabilities, embedded VOIP (voice over Internet protocol) 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.