IBM has used the opening of the annual Mac jamboree in San Francisco to plug a version of its new Lotus Notes 8.5 collaboration software to the steadily growing universe of Mac users.

Industry analysts calculate the Mac market share quietly crept into double digits during the last month of 2008, with the Windows alternative now accounting for 10% of the overall operating system market.

Similar to Notes 8 for Windows and Linux, Lotus Notes 8.5 has been tuned to help administrators achieve better storage savings than previous versions, and comes with a redesigned interface that arranges all sorts of collaboration and social networking tools on one screen in fewer clicks. It is also said to offer good levels of integration with public Web calendars

With the arrival of the new version it will also become possible for any licensed Mac Notes user to access the collaboration system remotely through their standard Safari web browser.

Notes 8.5 works well with Lotus Sametime software, IBM noted, a development that is intended to make for a richer experience for instant message and VoIP users.

The upgraded Notes software calls for the latest Leopard Mac OS X 10.5 operating system.

IBM also disclosed that its free office productivity software would become available to Mac users by the end of January, in the form of its Lotus Symphony document, spreadsheet and presentation suite.