Forrester reports open source database market at the point $850 million and predicts it a 40% growth (to $1.2 billion) by 2010.

Doesn’t compare to a $16 billion commercial database market, of course, but considering the absence of licensing costs, it’s still quite an number.

“More enterprises are deploying open source databases than ever before,” the report states. “Enterprises are mainly looking to open source databases to support new applications such as Web 2.0, Web-based applications, small portal applications, radio frequency identification (RFID), and other new workloads.”

The report continues: “Every enterprise should now consider open source databases as part of its overall DBMS strategy, as doing this will deliver cost savings, especially when supporting small to midsized applications.”

Forrester also estimates open source databases to be quite capable of supporting 80% of business applications market. The factors backing up this estimation include:

1) Price. Obviously, open source is more cost-effective that commercial. Forrester estimates cost savings ranging from 20% to 55%.

“IT costs themselves have gone up quite significantly over the years, and database management costs have also grown over the years,” said Noel Yuhanna, a Forrester analyst and the report’s author. “[Companies] are looking to contain these costs, and they’re looking for alternative database options, including open source.”

2) Flexibility in use and deployment, which again substracts from the general cost.

3) The large number of independent software vendors and partners, providing a 24/7 support.

That doesn’t mean, however, that companies currently using comercial databases should switch to open source momentarily. The migration process can get complicated, so much thought should be given to a decision like that.

“Migrations are complex, and no one actually has a solution where you can do a 100% migration from an Oracle database or DB2 to an open source database so easily,” Yuhanna said. “It takes a lot of effort, and basically no one wants to spend a million dollars to save a million dollars.”

For more info and to get open source DBMS deployment advice, see this article.