A new IDC study has said that the growth in adoption of standalone open source software is accelerating and that the total market will be worth $5.8 billion in 2011.

The market reached $1.8 billion in 2006, and will grow 26 percent annually for the next four years, the firm predicted.

The study is a relatively unusual effort to treat the sprawling, quick-changing open source software market as a serious business, and indicates the growing business acceptance of open source software.

IDC found that the open source market is in a significant stage of growth, as previous barriers to adoption fall away.

This is particularly true in the business world, where companies are waking up to the fact that open source opens up more choices and gives them something to use as a bargaining chip with proprietary software vendors.

Companies are also becoming more comfortable with subscription revenue as a business model, something common among open source companies, while larger enterprises are also getting on board.

Financial backing from venture capitalists is helping boost growth, IDC said.

Software distribution is growing, but revenues will take longer to follow suit, researchers found. That's partly because much open source software is free, while other products use a subscription revenue model rather than getting users to pay a lump sum up front.