It's also unusual in that it has been able to fund itself as it grew. Tech companies usually seek several rounds of investor funding as they need cash to pay for their next phase of growth (or even just to stay afloat) but Atlassian was founded 13 years ago with A$10,000 of credit card debt and while it has sold existing shares, it has never had to raise funds.
It's this that has allowed founders Mike Cannon-Brookes and Scott Farquhar to retain about a third of company each, worth more than A$2 billion each.
The pair's initial ambition was a lot more modest. When they started the company after graduating in computing from the university in Sydney, they wanted to earn A$48,000 a year. This was what PwC was paying graduates and they wanted to match that without having to put on a coat and tie.
Atlassian is also unusual in that it employs no salespeople. It relies instead on word of mouth and its roster of clients includes Nasa, Audi, Telstra and Virgin Media. Farquhar says this is one of the reasons for its success - instead of spending time and money on developing sales channels, it was able to put all of its focus into better products.
This means that unlike a lot of the other unicorns - the nickname in the finance world for a tech start-up with a valuation of US$1 billion or more - Atlassian has been profitable for the past decade.
At a time when many investors are shunning overpriced emerging tech firms going public, Atlassian's IPO was "substantially oversubscribed" by big US mutual funds, according to reports.
Atlassian has listed on the US Nasdaq technology exchange. "We do not expect to declare dividends in the foreseeable future," the company says it its prospectus. "We currently anticipate that we will retain future earnings for the development."
This is akin to sacrilege in OzAustralian investors want a steady stream of dividends and are less likely to support a company which won't be paying them.
US investors, by contrast, are much more comfortable to let their companies reinvest their earnings in the hope that they will keep growing.
Apple, for instance, floated on 1980, but didn't pay a dividend until 1987. What's more, it suspended its dividend between 1995 and 2012.
To say that investors didn't lose out from that policy is somewhat of an understatement. Those who spent US$990 at Apple's initial public offering in 1980 would have got 45 shares at US$22 each. After several share splits (where a company transforms one share into two or more shares) that investor would have 2520 shares today, worth a little under US$300,000
Sadly, things probably would have played out differently in Australia. Investors would have lost patience and sold down the stock. With the share price falling, fund managers worried about the current quarter's numbers would have put pressure on the board to fix the problem. The dividend would have been restored at the expense of innovation and long-term growth.
The end result would have been no iPod, no iPhone and no iPad - and quite possibly no Apple.
