"Open-source and free [databases] demonstrated to us that there is an opportunity among a broader community of developers and solution providers than we had historically been reaching," said Bernie Spang, IBM's director of data server marketing.

Murphy said IBM's move would more likely affect open-source databases such as MySQL or Ingres used by smaller companies than "steal users away from Microsoft and Oracle."

But Peter Yared, CEO of ActiveGrid Inc., a San Francisco-based provider of tools for businesses using the LAMP (Linux, Apache, MySQL and Perl/Python/PHP) stack of open-source software, said that a free DB2 is a "nice blocking move" against open-source databases, which big corporations are increasingly adopting for Web server farms and similar applications for cost reasons.

"For big IBM DB2 shops, this lets them use the exact same SQL throughout their back end," said Yared, whose firm is bundling the DB2 Express version with its next software release. "For IBM, it lets them prevent other databases from getting a foothold into its accounts."

IBM previously waded into the free-database waters by open-sourcing Cloudscape, a lightweight Java database it picked up through its Informix acquisition. IBM turned Cloudscape over to the Apache Software Foundation, which now develops the software under the Derby name.