Wired on Friday: It's not often that the editing of a piece of legal boilerplate 3,000 words long requires a grand unveiling at a two-day conference, heated discussion across the globe and a solemn declaration that nothing will be done with it for over a year.

But then, the general public licence (GPL) version 3 is not just any bit of legalese. It's the long-awaited sequel to one of the key documents in the world of open-source or free software - an ingenious bit of legalistic aikido that turned traditional copyright on its head.

Every Linux-driven webserver you've ever visited (and, if you wander the web at all, it will be quite a few) has a copy of it buried somewhere on its drives. Much of the free software that drives the internet is distributed according to its rules - and more importantly, every piece of software derived from that original software.

Rewriting it, as one law professor has said, is like hacking the very constitution of the free software movement.

What the GPL does, and has done for over 16 years, is provide an odd bargain on some software products.

If whoever owns the copyright to a piece of software decides to place it under the GPL, the usual restrictions of copyright vanish and the GPL lets anyone copy the work as much as they like.

But here's the catch: if you make any modifications, you have to make the changed work as free to distribute as the original, and you have to agree to distribute a version of the software in a form that makes it easy to modify, and hopefully improves it - the "source code" of the program.

It's as though a group of bakers decided to offer, with every one of their cakes, the recipe to make it, together with the requirement that anyone who made a cake with their recipe should pass on the secret to the person they sold their cakes to.

If that sounds like a political or ethical act rather than a legal one, you'd be right. The GPL's author, Richard Stallman, created the licence to combat the decline in knowledge-sharing among programmers. It was a moral crusade for him.

However, over time, others argued, the evidence appeared to show that free software, aside from its morality, had quality advantages too.

Like the free exchange of ideas in academia, or peer reviews in science, the co-operation created by licences like the GPL appeared to make for an industrial-quality and widely supported code.

And, by enforcing sharing, the GPL also carved itself a neatly altruistic niche in the cut-throat commercial world. No commercial company could hijack the code for its own use without simultaneously revealing its additions to its competitors.

Despite a fair degree of muttered criticism by lawyers about its vague drafting, the GPL has survived longer than most licences - and has never been successfully challenged in court. But the threats to Stallman's moral-free software movement have grown, and the qualms of those who now build sizeable businesses supporting and improving open-source have never quite abated.

And so, after much discussion, Stallman's lawyer, Eben Moglen, this month unveiled version 3 of the licence, the first update since 1991.

Amazingly, in the powder-keg flammable world of lawyers, political hotheads and armchair critics - which make up much of the new world of open-source - they seem to have got away with it.

That's not to say that the changes aren't major. If the new GPL is adopted by individuals and companies, they'll be taking on two extra parts of the free software crusade.

First, the new licence makes it clear that open-source software is not to be used in digital rights management (DRM) systems, like that used by Sony BMG and Coldplay's publishers to copy protect their CDs.

DRM is ethically at the opposite end of the spectrum to Stallman and the free-software movement, preventing the users of software from changing, improving or even re-distributing it.

More dangerously, DRM could be used to bypass the GPL's free distribution requirements, so DRM and the GPL now part company.

The other additions are not quite so strongly stated. Many have complained that the old GPL was inflexible, and ironically could not itself be altered without making it incompatible with differing versions. That has been fixed, by those explicitly using the licence to alter it in clearly defined ways.

How those new variants propagate will be an interesting story in itself. Moglen and Stallman now let software authors be a bit more demanding in how they say future distributors of their software make the original recipes available.

Google, for instance, does not offer copies of the free software it uses because the original GPL only required that from companies distributing programs, not using them.

Adopters of the new GPL can stipulate that a link be provided to download the software used by a website.

And even stronger language is permitted to fight what the free software advocates see as their most dastardly enemy - software patents. No software is truly free if users can be sued by strangers for the violated patents it might contain. The new GPL lets users have some protection by stipulating that suing types can't use the software themselves. And others can add clauses to strengthen that retaliation by ganging up the threat with other software makers.

The GPL was always a bargain between ethics and pragmatism. Now that the pragmatists include multibillion dollar companies like IBM and Novell, it'll be interesting to see if Moglen and Stallman's additional scruples make the grade.

They may well do. The free software movement's founders may speak softly, but they carry a big stick.

And it's a stick that IBM and Novell have learnt packs quite a punch.