Oracle, whose database software has made the company billions, released a free version of its database to compete with the increasingly popular free products from MySQL.

The free beta version of Oracle Database 10g Express Edition, or Oracle Database XE, is available for download today, the company said in a statement. XE was created to give software developers, database administrators and students a sense of what it is like to run their applications on Oracle code.

XE is built on the Oracle Database 10g Release 2 code base and is fully compatible with the company's Standard Edition One, Standard Edition and Enterprise Edition database products.

Users can start small. If they like what they see, they can upgrade to other editions of Oracle Database 10g as demand grows, moving their applications to other editions without changes.

XE delivers the same SQL and PL/SQL interfaces that are available in Oracle Database 10g, as well as support for Java, .NET, PHP, and Windows. XE also lets developers take full advantage of Oracle's HTML DB feature for Web application development.

Oracle Database XE is available now on 32-bit Linux and Windows operating systems, and can be installed on any supported hardware platform.

The software uses one CPU or one dual core of processing capability; has below 1 gigabyte (GB) of memory; is limited to a single instance per system; and stores up to 4GB of user data.

Oracle said third-party providers can distribute or embed XE with their products as long as they adhere to the above criteria. For example, Novell and Red Hat will offer their users access to XE.

Oracle's move is a clear shot across the bows of open source database vendors, such as MySQL, which makes popular database software products used in workgroups or departments of large companies.

Oracle Vice President Thomas Kyte took a dig at smaller vendors in the statement: "No one has to make do anymore; everyone can now start with the best."

XE is an answer to MySQL 5.0, which launched last week.

While Oracle has simplified its software somewhat to lure students or casual developers, MySQL has regularly upgraded its flagship database to become increasingly enterprise-friendly.

MySQL 5.0 is designed to help relational database systems (RDBS) administrators both use and transition to MySQL.

It features a graphical user interface (GUI) migration toolkit to migrate data to MySQL from Microsoft's SQL Server and Access database applications, as well as Oracle's 10g lines.