Nat Torkington stirred up some controversy when he asked, "Is 'Open Source' Now Completely Meaningless?" He has a good point, however. With so many companies claiming to be "open source" -- despite seemingly disparate business models and licensing schemes -- it's getting hard to tell what is legitimate open source and what isn't. The mere fact that so many voices have begun to weigh in on the issue is proof of how murky these waters have become.

When asked to explain what open source software is, most people are likely to rattle off a list of practical characteristics of the software itself. But upon closer examination, it's very difficult to explain the value of open source in this way.

For example, open source software is free of charge. If it's open source, you can be assured that somewhere there exists a version of the product that you can download and mess around with for no cost. But software vendors give away lots of high-quality, polished, enterprise-ready software, too. Microsoft Internet Explorer is "free," by this definition, yet it most certainly does not meet anyone's concept of open source.

Similarly, open source software is said to be driven by "community," but it has no monopoly on this concept. Adobe Photoshop and Microsoft Excel, for example, offer community in spades. You can find just as many free classes, mailing lists, Web forums, user groups, books, magazines, and chat rooms devoted to these products as you can for Linux or any other open source software. What's more, each has its own thriving network of independent developers that produce add-ons, templates, and plug-ins, many of which can be downloaded for free. So to say that "community" is the defining characteristic of open source seems only to cloud the issue.

It's true that open source can be redistributed by the end-user, but that's not a defining characteristic of open source, either. In practice, lots of no-cost software is redistributable. I have never heard it said that Microsoft has taken action to prevent independent VARs or contractors from burning DVDs full of Windows software updates to distribute to their clients. Nonetheless, those updates are proprietary software. Distributing someone else's software doesn't make it open; it just makes you a courier.

So what of the most glaringly obvious characteristic of open source: The fact that the source code is available to the end-user? Is that enough to define "open source" as a category? Unfortunately, the answer is still no. Microsoft's Shared Source program makes Windows code available to select customers but does nothing to change the status of Windows as proprietary software.

It's clear, therefore, that the practical characteristics of open source software don't do a very good job of explaining what open source is all about. So what is it really? The answer to that question is complex, but fortunately it is well documented. It exists in the definition of open source as published by the Open Source Initiative and in the wording of the numerous OSI-approved licenses under which open source projects are published.

According to perennial open source gadfly Richard Stallman, however, those definitions are part of the problem -- and I think Stallman has a good point, too. In a new version of an essay posted on the Free Software Foundation Web site, Stallman points out that "open source" misses the point of free software.

"The term 'open source' quickly became associated with the practice of citing only practical values, such as making powerful, reliable software," Stallman writes. "Most of the supporters of 'open source' have come to it since then, and that practice is what they take it to mean."

To Stallman, open source is merely a subset of what he calls "free software." In fact, he says, "The main initial motivation for the term 'open source software' is that the ethical ideas of 'free software' make some people uneasy." By extension, this is also the reason why it can be difficult to get any two people to agree on what "open source" really means. Without a well-defined ideology to guide it, the open source movement can be seen as essentially rudderless.

Free software is clearly an ideological movement, and as such it will naturally make some people uneasy. But a growing number of commercial software companies have begun to accept the Gnu GPL (General Public License), the most important expression of the free software ideology. Alfresco's vice president of business development (and InfoWorld blogger) Matt Asay even goes so far as to suggest that software companies need the GPL.

So maybe the question is not whether "open source" has become meaningless. Maybe the real question is, why we are still talking about it at all? There's a truly revolutionary way of producing software out there. It's called free software. Maybe it's time more of us started calling it what it is.