Cut through the partisan politics, the ponytails and the free-flowing anti-Microsoft vitriol, and the open source community has a lot to say for itself, both politically and practically. Enthusiasts emphasise that the open source approach to developing cost-free software has created a Darwinian environment in which the best quality products (whether open source or commercial) will win - not restricted by superficial marketing deadlines and encouraged by the importance of peer recognition.

Some of the fruits of its labour - Linux, Apache, FireFox, MySQL, JBoss - have proved to be resounding successes; certainly cheaper, often more reliable and in some areas more secure than their proprietary counterparts. In plenty of other areas, especially at the two ends of IT - the desktop and high-end servers - there has been nowhere near the same level of penetration.

On the office desktop, for example, Microsoft still reigns supreme. Open source PC applications show the kinds of shortcomings that might suggest the highly technical developers behind many such products feel they will get considerably more peer recognition by developing systems software for the cognoscenti, rather than applications software for a broader, less-savvy audience.

Further, broader, deeper

The patterns of take-up of Linux certainly underscore confidence in that system's software development effort. A June 2005 survey by Forrester Research found that 56% of the 137 large North American companies its analysts talked to were already using Linux and a further 19% had plans to use the operating system in key projects. This compared with 46% using and 14% planning to deploy Linux at the same time in 2004.

Although this does not illustrate the extent of usage within these organisations, it is still testament to the fact that a majority of large businesses have experience with Linux and, based on that experience, are upping their commitment - a fact underscored by revenues for Linux (servers, PCs and packaged software) heading towards $35.7 billion in 2008, with a compound annual growth rate of 26%.

While Linux has become the undisputed third option, the alternative to Windows and Unix, it is not alone in its penetration of corporate IT. It is now credible to talk about the open source stack, says Marten Mickos, CEO of database server provider MySQL. "A few years ago, 'open source' simply meant Linux. Big corporations would go for Linux, but stop short of the full stack. Now there's the full stack of software for the operating system through to the applications." He cites the widespread acceptance of the LAMP software bundle as pushing open source through the enterprise. LAMP is based on the operating system Linux, the web server Apache, the MySQL database and the PHP programming language. It is estimated that over half of all open source software developers use LAMP as their base.

While no-one doubts certain open source packages have found their way into the data centre, it has not typically ousted core commercial products. Matt Asay, director of open source strategy at software vendor Novell, estimates that 35% of servers are Linux-based. But Claude Buellens, European director of the Open Source Development Labs (which also employs Linux inventor Linus Torvalds) reckons that up to 80% of Linux servers are "on the edge" of the data centre, involved in external communications, such as email and web serving, where businesses are more likely to experiment.

However, commitment has varied across organisations of different size. "Small and medium sized business [SMBs] are seeing what the big companies are doing and then moving in," says Tim Yeaton, senior VP of marketing at open source provider Red Hat. Of the 308 European SMBs Forrester surveyed in a report entitled 'SMBs Accelerate Open Source Adoption', 28% of those with 500 to 999 employees thought it was either 'very important' or a 'critical priority' that their IT organisation moved more systems onto Linux.

Within larger organisations, open source has generally been adopted for basic but high performance applications and then, in some cases, assimilated into more mission-critical areas like enterprise resource planning (ERP) and the supply chain. Survey results support that increasingly central role. A study of 300 companies by managed hosting provider Rackspace found that Linux was deemed 'better' than Windows for the majority of a set of 12 core business applications. In only three areas - enterprise/back office applications, rich client corporate email and streaming media - did their customers rate Microsoft better than Linux. The remainder, which included high and complex transactional applications, websites and database intensive applications, were deemed to run better on Linux.

Successful deployment of open source applications in select areas naturally encourages organisations to think about expanding its use elsewhere. Brian Bullen is the Unix Systems Administrator at Stirling University, which has recently migrated its SAP application servers over to Red Hat Enterprise Linux. He explains that the university had been using open source for some years. "We started with web servers and then moved onto things like DNS [domain name system], email routing and virus scanning and web filtering. Of course our largely positive experience is one reason we had the confidence to pursue the Linux route for SAP application servers."

For analysts such as Michael Goulde of industry analyst house Forrester Research, Linux is the leading indicator for expanded open source use. "Once Linux is in the door, adoption of other open source technologies will continue to expand," he says.

Desktop deficiency

However, there are still some no-go areas for open source - at least for some users. In August 2005, the Central Scotland Police (CSP) force announced it was returning to using Microsoft Windows after a five year foray into Sun's StarOffice. CSP found that communications between its staff and other police forces were hampered by incompatibilities between StarOffice and the near-ubiquitous MS Office.

Furthermore, what is normally seen as a strong point of open source - the ability for organisations to adapt the source code for their own purposes - became burdensome without a sufficiently large or skilled in-house team. David Stirling, the head of ICT at CSP says: "For desktops, open source software can have a short lifespan and it needs a lot of configuration. The size of our department means we can't afford to have people spending a lot of time putting in bespoke systems. At the end of the day, we are a policing organisation, not an IT one."

As that suggests, CSP was out on a limb. Annette Jump, principal research analyst at market watcher Gartner, explains that just 1.8% of all professional desktops worldwide run open source software, although she expects that to increase to around 3% by 2009. Windows by comparison is installed on around 95% of PCs. "The main reason why Windows is so dominant is the cost of migration," she explains. "Companies use so many applications and most have to be completely rewritten when moving over to Linux. Generally, migration only makes sense for users who run one or two applications, isolated from the rest of the company like call centre workers."

Despite such considerations, there are still businesses keen to move away from the Microsoft desktops. "We won't look at something if it's completely closed," says Roland Whitehead, CIO at Bonhams auctioneers. "We might still run Microsoft on the desktop, but we have an internal bet that we won't install their next offering [Windows Vista] and that by the time they release Vista we'll be installing Linux on our desktops." Vista is due to ship at the end of 2006.

Whitehead has undoubtedly reaped financial benefits by using Linux: "We have spent a fraction of what our competitors have, because instead of having expensive CRM and ERP systems, we've developed from the ground up combining open source and proprietary solutions."

A low or negligible entry price plus a lower total cost of ownership are the main reasons behind open source adoption, according to Forrester's Goulde.

Nevertheless, he advises against cost being the central motivation behind migrating over to open source since expectations are not always realised. Of the North American companies he surveyed, 18% said that the operational management of open source software was more complex and expensive than expected, and a further 12% said the anticipated cost savings never materialised.

Open source vendors like to concentrate on the other 85% who have eliminated expensive licences.

"Previously there were no [quality] requirements on software," says MySQL's Mickos. "Companies could sell crap for high prices. Now [because of open source] the requirement level has gone up." But rather than quality, concerns over support are the single biggest barrier to the adoption of open source software in the enterprise. Companies are concerned that problems they have - with implementing code, with bugs, with security patches and so on - will not be addressed by the 'community' and that the skills at third-party open source service providers will be lacking. Goulde thinks such fears are normally based on "impressions, misinformation or biases", given how aggressively companies such as HP, IBM and Atos Origin have embraced open source support.

The other main challenge will be the very real one of Microsoft's hegemony. Not only are customers used to the Windows look and feel, they can also expect the parallel functionality in open source products. Mickos argues that sometimes simpler, more elegant and faster is better - and that means not trying to fulfil expectations by mimicking the 'legacy' world of Microsoft. "We're not here to please customers," he says.

That reflects a new bearish attitude among open source companies. Linux has proven the model and instead of dismissing open source, Microsoft and many others in the commercial world of software are responding with new packaging and pricing. But it will take more than that to disrupt the pattern that has now been set: what has happened in operating systems, web servers and browsers could eventually happen in many other areas of the software stack.