For years, the battle between the open source movement and Microsoft bordered on religious warfare. The two sides fired increasingly aggressive shots at one another – from the software goliath's boss, Steve Ballmer, calling open source "a cancer", to the man behind Linux, Linus Torvalds, suggesting that he might "destroy Microsoft" without even trying.

It was a conflict that looked like it could continue for generations. But now, according to one leading voice, the arguments are settled – and the opposition posed by Bill Gates, Ballmer and their followers is untenable.

"If I look at it with some perspective, I think that they are fighting a rearguard action," says the investor, philanthropist and campaigner Mitch Kapor. "The battle is over."

He continues: "At the detailed level, there are a million issues to work out – but will open source kill software? Nobody's saying that."

That may come as news to some who have resisted the open source movement – as recently as last year, Gates claimed that the fundamentals of the open source philosophy meant that "nobody can ever improve the software" – but Kapor has more experience than most of those who have stepped into the fight.

Resistance is futile



At the time, Kapor helped to convince AOL that it should jettison the Netscape browser it had bought and turn Mozilla into a separate non-profit operation. Indeed, he invested $300,000 of his own money in the push to create a viable, open alternative to Microsoft's massively dominant (and heavily criticised) Internet Explorer browser.

Since it launched in 2004, Firefox has chipped away at Internet Explorer's market share and established itself as the world's second most popular browser. But while attacks on open source still make Kapor's blood boil, he suggests that the bigger picture indicates that resistance is futile.

"What's remarkable is that nobody remarks on it, because a few years ago people were virtually pulling out their guns to shoot at each other – and now it's a settled matter, as I read it."

While Firefox is widely regarded as a huge success, Kapor warns that it is not actually the best example of the victory of open source. Instead, he suggests, the movement's main achievement actually lies out of sight – amid the systems that underpin the web itself.

"I tell people that the history of Mozilla and Firefox is so one of a kind that it should not be used – ever – as an example of what's possible," he says. "The accomplishment of open source is that it is the back end of the web, the invisible part, the part that you don't see as a user."

"All of the servers, pretty much, they run Linux as the operating system; they run Apache as the basic web server on top of which everything else is built. The main languages out of which web applications are built – whether it's Perl or Python or PHP or any of the other languages – those are all open source languages. So the infrastructure of the web is open source ... the web as we know it is completely dependent on open source."

The reliance goes both ways, he suggests, meaning that the web and the open source community are interdependent. While developers and dotcom companies have turned in large part towards open source technologies to build the future of communication, it is the web itself that has made such an approach possible.

The sort of large-scale, highly distributed teams that are the hallmark of such development – teams of coders spread out around disparate parts of the world – rely on websites to share code, discuss ideas and meet each other. What started as a marriage of convenience has now turned into a symbiotic relationship.

"Without the internet and the web, no open source – without open source, no internet or web," he says. "So they co-create each other."

The reasons for this shift from a fringe ideology that could spark warfare among programmers to an accepted, everyday part of hi-tech life are complex. But Kapor puts at least part of it down to an important evolution in the underlying philosophies that emerged, appropriately enough, with Mozilla back in 1998.

After Firefox's predecessor, Netscape Navigator, was crushed by Microsoft, its owners decided to release the source code, which became the Mozilla browser. Kapor gives credit to those who originated and then developed the concepts that led to such acts, including free software campaigner Richard Stallman and Torvalds.

Their influence and ideas helped build and then reshape the idea of free and open software development, taking it from its doctrinaire beginnings through to something that was more palatable for commercial companies.

"If the rules of the game that were established by Stallman about free software – which were commercially unfriendly – had not evolved, we wouldn't have Firefox and we wouldn't have the web," Kapor says. "But the culture evolved to be less restrictive and more permissive – the idea of open source licences that permit but don't require new contributions, additions to be made available to everybody."

Declining empires



While there is no guarantee that they will stick to those ideals in the long term, Kapor is now optimistic that the movement will have more staying power than whichever company happens to be the flavour of the month.

"I've been around long enough to know that empires come and empires go, and I can't tell how long the Google empire is going to last – but I'm pretty convinced that the answer is less than forever.

"Microsoft still has a big empire, but when Steve Ballmer thinks a new thought, the world doesn't tremble the way it used to when Bill Gates had a new thought," he says. "That day is over, and it will be over for Google. Facebook may be the next, or Twitter or somebody you haven't heard of, but empires come and empires go."