SYDNEY, Australia — Atlassian is a very boring software company. It develops products for software engineers and project managers, with hits like Jira (for software project management and bug tracking) and Fisheye (a revision-control browser). And who could forget Confluence (an enterprise knowledge management system)?

So why are its two founders household names in Australia?

Because Scott Farquhar and Mike Cannon-Brookes, both 39, are the country’s first start-up-to-I.P.O. tech billionaires. And because in the last year, they have started to make noise.

Until recently, they largely stayed out of the public eye, even as Atlassian grew to become a $20 billion company. Now, as Australian politics tilt toward the right on global issues like immigration, cybersecurity and climate change, they are emerging as new political voices, getting in Twitter spats and lobbying Parliament.

The other reason they are now household names: In 2017, Mr. Farquhar bought the most expensive home in Australia, a historic Sydney estate that sold for 73 million Australian dollars, or $52 million.

In December, Mr. Cannon-Brookes broke that record when he closed on the house next door.

I met the Atlassian founders for a few days in Sydney. Over brunches, a ferry ride and a birthday party, they told me about their new roles in public life, and what it feels like to be the first tech billionaires in a country where wealth usually comes from mining or banking.

“People are interested now in what we’re saying,” Mr. Cannon-Brookes said. “We have a voice. We have a sense of responsibility.”

The two met as undergraduates at the University of New South Wales, where both were in a business scholarship program sponsored by Australian companies. They were encouraged to join one of those companies after graduating, but instead the two friends founded Atlassian, shocking their teachers and friends.

It was 2002. Doing a start-up was unusual.

“It was disbelief, really — why would you not go with a sponsor company?” said Christine Van Toorn, the program’s director and a lecturer at the school.

They relied on credit cards for initial financing. They advertised by going to developer meetups, buying beer for the room and putting Atlassian stickers on the bottles.

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Mr. Cannon-Brookes’s father was the chief executive of Citigroup Australia. His son wears his hair long, usually under a trucker hat. He has a shaggy beard and swears casually.