What's good for the U.S isn't good enough for the European Union. A week after the Justice Department cleared the way for Oracle (NASDAQ:ORCL) to complete its proposed $7.4 billion acquisition of Sun Microsystems (NASDAQ:JAVA), EU regulators yesterday opened an antitrust inquiry.

The European Commission gets until Jan. 19 to review the deal, giving Sun just enough time to report another lousy quarter. Oracle, meanwhile, gets more time to decide what to do about Sun's server business, which is badly lagging peers such as Hewlett-Packard (NYSE:HPQ) and IBM (NYSE:IBM).

EU regulators will spend little, if any, time pondering the hardware side of this deal. They're more concerned with MySQL, the open-source database that Sun purchased for $1 billion last year. They want to ensure that MySQL customers won't pay a price as a consequence of Oracle's ownership.

"[What happens] when the world's biggest proprietary database company proposes to take over the world's leading open-source database company," The New York Times quoted competition commissioner Neelie Kroes as saying.

MySQL is a crown jewel of the open-source community, a database that has proven popular with developers writing code for the Web. Oracle is more attuned to large in-house deployments, a segment of the market in which its biggest competitors are IBM's DB2, Microsoft's (NASDAQ:MSFT) SQL Server, and Teradata (NYSE:TDC).

Sun, in acquiring MySQL, had hoped to win more enterprise deployments -- using software to lead to hardware sales. The company's recent results don't speak well of that strategy.

Nonetheless, the EU seems likely to insist that Oracle guarantee further development of MySQL as an open-source database and not stunt its growth in the enterprise. The best way to achieve that is via some sort of independent entity, such as a standards committee. Or, better yet, a sale.

Red Hat (NYSE:RHT) would be MySQL's ideal suitor. The company already drives most open-source infrastructures via its Linux distribution and JBoss application server, and has the capital and open-source reputation to attract the talent needed to grow MySQL over the long term.

But all this assumes co-founder and CEO Larry Ellison would agree to concessions, and history shows he's not afraid to mix it up with regulators when he thinks he has a case. Either way, thanks to Europe, there's little chance of Sun setting before the dawn of 2010.

For related Foolishness:

Teradata is a Stock Advisor selection and Microsoft is an Inside Value pick. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Tim Beyers owned shares of IBM and Oracle at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy has an odd craving for carrots and celery today. Hmmmm.