Although IBM’s open-source support is no money-maker, it does serve as a deft weapon to undermine Microsoft’s markets

Big Blue collects about $1 billion a year in licensing fees from its hoard of 40,000 patents. So it came as quite a surprise to some on Jan. 11 when IBM pledged to make 500 of its software patents, valued at about $10 million, freely available to open-source software projects such as the Linux operating system and the Apache Web page server software. Why would IBM allow others to use its intellectual property free of charge?

In a word: Microsoft. The move is central to IBM’s efforts to fend off Microsoft and its Windows monopoly. While the computing giant will continue to innovate and gather new patents as aggressively as ever, at the same time it is stepping up efforts to bolster the world of open-source software. IBM figures that doing so will give it a leg up in selling the software and services that work with the open-source programs it helped develop.

And that in turn should help it gain an edge against its Redmond (Wash.)-based rival. “They’re poking their thumb in Microsoft’s eye,” says Alfred S. Chuang, chief executive of software maker BEA Systems, a competitor of both tech giants.