Sales of open source software will grow from $1.8bn last year to $5.8bn in 2011, analyst firm IDC predicts.

Matt Lawton, programme director for IDC's Open Source Software Business Models research programme, typified the current market as "immature" and in the "early stages".

The projected revenue figure is low when compared to commercial, closed source software. But the analyst believes that revenues alone do not reflect the actual distribution of open source software.

Proprietary software typically charges an upfront fee, while open source charges only for support and typically does so on a pay-as-you-go basis.

IDC cited culture and comfort levels as the primary drivers behind open source software.

The development model has gained credibility because venture capital investors are increasingly backing the software.

Companies have become more comfortable with subscription models such as those pioneered by Red Hat.