Is the WikiLeaks founder a freedom fighter, a naive libertarian or a zealot with a messiah complex? Those who know and have worked with him seem unable to agree

A posed photograph makes for an easy manifesto. The sight of Julian Assange wearing a leather coat and an expression that wouldn't look out of place in a spy thriller may have summed up, for many people, what they think of him – someone who is dedicated to uncovering the evil that people do, who has a clear and unwavering moral code, and who has worked out all the answers.

Not exactly, say those who know and have worked with Assange. "His philosophy keeps evolving," one person who has met him a number of times says. "I don't think he's quite sure himself."

Another says there is something of the "naive libertarian" in Assange's approach. "He makes that connection between government and conspiracy. He really does think that WikiLeaks is going to change the world … he constantly expects that it will achieve change through telling the truth."

But to others, Assange is just a zealot with a messiah complex. "You behave like some kind of emperor or slave trader," Daniel Domscheit-Berg, a former WikiLeaks spokesman, said in an online chat this summer. Assange – who had been using the conversation to try to find the source of leaks from inside the organisation – suspended him on the spot, and Domscheit-Berg left the group in September.

WikiLeaks is a loose online organisation whose members work on computers all over the world, using Skype and encrypted online chatrooms to work out what they'll do next and co-ordinate their protection from angry authorities of all stripes. And Assange, nominally its leader, will pitch into the software development of the server architecture or security.

But what does he want it to achieve? Search the web and you'll quickly find a manifesto he published in December 2006, the month WikiLeaks began distributing documents, starting with the leak of a Somali sheikh's order to assassinate government officials.

Western media didn't notice, but it was a statement of intent – this was a site that would root out the truth.

"Every time we witness an act that we feel to be unjust and do not act we become a party to injustice," the manifesto said. "Those who are repeatedly passive in the face of injustice soon find their character corroded into servility. Most witnessed acts of injustice are associated with bad governance, since when governance is good, unanswered injustice is rare.

"Modern communications states, through their scale, homogeneity and excesses, provide their populace with an unprecedented deluge of witnessed, but seemingly unanswerable injustices."

Read on, and it gets hazier, filled with looping rhetoric, "collaborative secrecy, working to the detriment of a population, is enough to define their behaviour as conspiratorial", it asserts, before asking: "What does a conspiracy compute?". But its clear message is that governments with secrets should be seen as conspiracies, in themselves, against populations – if you remove the ability of conspiracies to exist then you can get rid of governments' ability to oppress people.

In many ways it sounds like an idealistic computer hacker's manifesto – "information wants to be free". That's not surprising, because Assange was one from his teens.

Born in July 1971, he led a peripatetic life (his mother, who campaigned on a number of causes, was in a touring theatre group) and, in the 1980s, went by the "handle" – a hacker's online monicker – of Mendax. In a co-authored ebook about the Australian hacker underground, he describes faking office noises on a tape and pretending to be much older than his 16 years to get passwords out of people, a process hackers call "social engineering".

He graduated to hacking into US military systems, where he found documents suggesting that US military hackers had targeted their own systems to see how weak they really were. If they could do that, what about targeting other countries? The idea horrified him.

The police raided him in 1992, and in 1995 and 1996 he pleaded guilty to a total of 19 hacking charges and was released on bond. Perhaps significantly, during the case one of his two fellow hackers – the Internet Subversives – turned crown witness against him.

A lengthy battle with his former wife over custody of their child prompted an early desire for civic transparency by getting access to otherwise secret Australian legal records about custody.

Other reports suggested he and two others had formed a civil rights organisation to "fight corruption and lack of accountability" in the Victorian state government in the 1990s.

It's fairly easy to join the dots to the modern day. Assange registered a domain called leaks.org in 1997 but said he "didn't do anything with it" and co-developed a piece of cryptographic software called Rubberhose, which would to hide multiple sets of data on a single piece of storage such as a thumb drive.

Its intended users were human rights workers who could credibly deny that the other data existed, even under torture. As Assange noted drily: "It's nicer, particularly given the frequency of equatorial despotism, to be tortured in the computer room." (Why "nicer"? Because there would be air conditioning.) Then there was a spell of programming, some time at university in Australia, and then WikiLeaks.

Reading his self-penned history, you glimpse the hacker's willingness to spend hours trying to break into systems, and also get used to the hacker's thrill of getting "root" – top-level access so you can see and change anything you want – on remote computers.

In a sense, WikiLeaks is trying to "root" governments. But the hacker's pleasure is lonely: sharing the knowledge of your achievement is dangerous, because it will attract the police. In its early days WikiLeaks was faceless even as it shared the pleasure of its finds, but Assange has said he realised it needed a public face. And, once more, he finds himself being pursued.

The erosion of trust he suffered through his co-hacker in the 1990s may explain what seems like paranoid behaviour today – constantly changing phone, insisting that people travel to secret locations, always attempting to throw off any pursuit. Even when arrested by the police, he refused to give a photo, DNA or fingerprints. "A rebel always," said Heather Brooke, the campaigning journalist, who covered his hearing.

But then, he has made powerful enemies. His laptop bag with three (encrypted) computers went missing on one flight. He is convinced it was done intentionally.

"Hackers, in general, treat people rather like machines – they just want to test their boundaries," says one person who knows him. Assange's new-found notoriety has presented new and dangerous challenges there.

The notion of radical transparency – turning governments inside out – is a popular meme among hackers. Often, it's government machines that they break into (because they're less well protected than commercial ones, and have more interesting stuff than home ones). WikiLeaks is an extension of that idea, with added ethics: not all of the fruits of hackers' work necessarily appear on the site, so that it performs both collection and filtering.

It is starting to catch on. The US, UK and Canadian governments have raced to embrace the idea of open and free data, though their commitment noticeably stops short where the release of names is involved. Accountability stops at the front door of the respective ministries, and doesn't tunnel into the individual offices.

WikiLeaks, and a new generation of "leaks" sites, want to go further. "It's like the Guardian's open data or freedom of information campaigns turned up to 11," another person who knows Assange says.

The next to join Assange in tunnelling into government may, strangely, be Domscheit-Berg: on Friday, he announced the creation of OpenLeaks, which he says will act only as the receptacle for leaked documents – the leaker will be able to designate which media organisations can publish the details.

"We won't publish any documents ourselves. The whole field is diversified," he told Forbes. "No single organisation carries all of the responsibility or all of the workload." If the designated organisation doesn't want it, the leak will just go out.

It doesn't sound quite as safe as WikiLeaks, where editors have removed details that might identify people at risk from war logs and diplomatic cables.

That is because Assange's creation is such a different beast from what has gone before. "It's the first news organisation that relies on brown paper envelopes turning up in the post," says a person who has worked with the team. "And then they run with it."