Red Hat Inc. has invested an unspecified amount in open-source database vendor EnterpriseDB Inc., a sign that the Linux vendor may be worried about the implications of Oracle Corp.'s takeover of MySQL through its pending acquisition of Sun Microsystems Inc.

The announcement was made in a statement posted Tuesday by the Westford, Mass. database vendor.

Neither EnterpriseDB nor Red Hat immediately responded to requests for comment.

The move is notable because much of Red Hat's current popularity as a server platform is due to users looking to run the free MySQL on top of Red Hat as part of a LAMP (Linux Apache MySQL Python/Perl/PHP) server. EnterpriseDB sells a proprietary, Oracle-compatible database called PostgresPlus that is based around the open-source PostgreSQL technology.

The two companies had reportedly been edging towards each other for months. EnterpriseDB CEO Ed Boyajian is also a former Red Hat vice president.

Boyajian said in a News.com story that the investment, part of a $19 million Series C round of funding, was a "significant amount of money."

EnterpriseDB took a small investment from IBM a year and a half ago, as part of its move away from Sun Microsystems Inc., which at that time had just acquired MySQL AB. This time around, fears about the fate of MySQL after Oracle's takeover may have motivated Red Hat to hedge its bets by getting cozy with EnterpriseDB, said Gordon Haff, an analyst with Illuminata Inc.

Despite Oracle's promises to the contrary , some fear that Oracle will bury or weaken MySQL to prevent it from cannibalizing sales of the pricier Oracle Database.

Asay theorized that Red Hat's investment is a counterattack of sorts, pumping up EnterpriseDB as a low-cost challenger to Oracle and other expensive proprietary databases.

Though far less widely used than MySQL, the PostgreSQL that EnterpriseDB relies upon is also generally considered more suitable for large, enterprise workloads than MySQL. EnterpriseDB has had some success pulling away Oracle customers, claiming 225 paying customers as of its investment by IBM in March 2008.

Red Hat could also be responding to increased competition from other Linux vendors.

The just-released Ubuntu 9.10 Server comes integrated with MySQL.