PROGRAMS: Open-source operating systems such as Linux and Apache, which can generally be downloaded from the internet and adapted for use with other programs, have become a mainstream business tool.
More than half the world's websites now run on the Apache Web server and 57 per cent of companies polled by research company IDC used Linux to run a big application within their enterprise.
The popular view is that there are few restrictions on how open software can be used. But, like proprietary software, it is distributed with a copyright licence. While this may simply require anyone redistributing the software to acknowledge the original author, the most commonly used GNU General Public Licence (GPL) is significantly restrictive.
Some experts believe that, by integrating open-source software into their infrastructure, companies are wandering into a legal minefield.
The GPL predates the open-source movement. Created in the mid-1980s by Free Software Foundation founder Mr Richard Stallman, it was designed to help non-commercial programmers ensure their software remained free and would not be incorporated into the proprietary products of commercial software developers.
Mr Stallman devised a licence with a number of unconventional restrictions. "It says that if you distribute source under the GPL you cannot charge a software licensing fee for it but only for the cost of distribution," says Mr Jason Matusow, Microsoft's shared-source product manager.
"It says that if you distribute code under the GPL, you must distribute source with it; and it says that if you include any GPL code into a larger body of work, the whole body of work is then covered by the GPL."
This last condition is particularly controversial, as it means the GPL can "convert" proprietary software into open-source software, since any company incorporating licensed code into its software products is obliged to open up its code too.
In this respect, Microsoft argues, the GPL threatens the entire software industry.
Open-source advocates dismiss this as scare tactics. Moreover, an increasing number of commercial software companies - including Hewlett-Packard and IBM - combine open-source software with their proprietary products.
Managed effectively, the viral aspects of GPL can be contained, says Mr Scott Handy, IBM's director of Linux solutions marketing.
Nevertheless, the challenge of mixing proprietary and open-source software has wrong-footed some. IBM stumbled last year when it discovered it was distributing a software product that violated the GPL.
Such mistakes can be expensive. Two years ago Mr Matusow, a programmer at communications device developer Nvidia, incorporated into a commercial video driver a portion of code freely available on the internet without realising that it was licensed under the GPL.
"Nvidia incurred significant additional cost in rectifying the situation," he says.
Opinions vary, however, over the degree of legal risk posed by the GPL. Since the licence has yet to be tested by the courts, some question its enforceability.
This is not an issue for software companies alone, says Mr Paul Lambert, a lawyer at Matheson Ormsby Prentice in Dublin. "There is a very real risk for any company using open-source software and it won't be long before a contentious case comes to court."
Mr Eben Moglen, general counsel of the Free Software Foundation, disagrees. The GPL imposes an obligation only on those who choose to redistribute modified or unmodified versions of software outside their own enterprise, an activity that is deliberate and - for firms other than software firms - unusual, he says.
Nevertheless, any company using licensed software could be putting its intellectual property at risk, says Mr Matusow.
Mr Mikael Pawlo, of Stockholm law firm Advokatfirman Lindahl, advises companies to view the debate as a wake-up call. "Many programmers will download and use code without considering the licence issues," he says. "Companies really need to undertake regular audits of their computer programs and check the associated licences."
