If you had any doubts about Sun Microsystems' commitment to open source, it's time to set them aside. Sun put its money where its mouth is Wednesday, with the announcement that it would buy open source database vendor MySQL for a whopping US$1 billion. If the price tag set tongues wagging, however, it was no more tantalizing than the question that immediately sprung to the minds of IT managers everywhere: Now that Sun owns MySQL, what on earth does it plan to do with it?

Sun has toyed with the idea of a database offering of its own for at least two years. But in a market where basic relational database functionality is increasingly considered a commodity, competing successfully is no mean feat, even when playing the open source card.

Certainly, Sun isn't the first to try it. In 2001, leading Linux vendor Red Hat launched its own branded version of the open source PostgreSQL database, only to scrap the project a year later after deciding that servicing and supporting a database was not its core competency. Similarly, Computer Associates opened the source of the Ingres database in hopes of becoming a one-stop shop for customers in need of an enterprise application stack, but had little luck winning market share away from the likes of IBM, Microsoft, and Oracle. CA spun Ingres off into its own company in 2005, where continues to nurture a small installed base.

In his blog announcing the MySQL acquisition Wednesday, Sun CEO Jonathan Schwartz remains characteristically effusive. "Until now, no platform vendor has assembled all the core elements of a completely open source operating system for the internet," he wrote. "No company has been able to deliver a comprehensive alternative to the leading proprietary OS."

Yet CA's and Red Hat's experiences seem to discredit the idea that a stem-to-stern platform offering from a single vendor is what customers really want. Not to mention the fact that Sun already offers enterprise support for PostgreSQL, a competing open source database that is widely perceived as being technologically superior to MySQL. Schwartz reaffirmed Sun's commitment to PostgreSQL in a conference call Wednesday, causing some analysts to speculate whether the MySQL acquisition was anything more than a billion-dollar PR stunt.

But there may be method to Sun's madness. The considerable goodwill that MySQL has cultivated among enterprise customers could have benefits for Sun that technology alone never could.

"I think the answer is simple: ubiquity," says Andy Astor, CEO of EnterpriseDB, which markets a high-performance, commercial database product based on PostgreSQL. "[Sun is] a big company; to move their needle, they need to see millions of potential users, which MySQL provides."

According to the company MySQL's own estimates, there are already some 11 million active installations of the MySQL database worldwide. What's more, MySQL is virtually the de facto standard relational database for rapid application development, particularly for the Web. In future, as these fledgling sites mature and their needs broaden, they will become natural customers for Sun's enterprise support offerings.

Sun's new role as steward of MySQL is sure to ruffle feathers in the software industry, as well -- particularly at Oracle, which, with its recent acquisitions, increasingly competes with Sun in the enterprise application platform arena. In 2005, Oracle bought Innobase, makers of a plug-in component that adds advanced features to MySQL, in what was widely perceived as a competitive swipe at the open source upstart.

For his part, MySQL CEO MAYEN rten Mickos has repeatedly denied that his company's aim is to displace high-end databases such as Oracle's. And that's only appropriate; for those customers who demand Oracle's most advanced features, no other product will do. But Mickos's protestations verge on false modesty. On the low end, MySQL is an absolute pandemic, and it's already making headway into the mid-tier territory traditionally owned by the likes of Microsoft. That trend is only likely to accelerate with Sun's backing.

What is unclear, however, is whether Sun will take any steps to alter MySQL's license terms. Licensing and project governance have played key roles in MySQL's success, and as a result, MySQL's license policy is somewhat more restrictive than the one that Sun has used for the rest of its software portfolio.