Earlier this month the Hawaiian resident made it to Wanaka, where he met Te Araroa Trail Otago trustee and photographer Gilbert van Reenen.
Over the years, it has become Mr Osborn's habit to accept cups of tea from strangers.
If he had not done this on the Mackerel Forest Track in Northland, he would never have met a man called Mike and would have had to negotiate a 3km gorse patch on his own.
He has also learned to whittle his gear down to a sparse 3.5kg.
In this respect, he's quite different from Mr van Reenan, whose 1960s vintage tramping kit weighs 35kg to 40kg when fully laden.
"I love showing people my gear. There's some older trampers who still tramp in their 70s.
"Their eyes light up because they can extend their years of tramping," Mr Osborn said.
Every gram counts on long-distance walks, so he chose the latest outdoor technology and fabrics and eschews boots for socks and sandals.
He carries clothing, sleeping bag, a titanium cooker and 230g "Cuben fibre" Zpack tent in a small 200g "day pack".
Mr van Reenan can only marvel at how things have changed since the 1960s, when he began adventuring with a cotton tent.
"This is the tent that I used a lot in Fiordland. It was the ultimate in lightweight. It was made in Holland and it was half the weight of everything else.
"That was before they got into aluminium," he recalled.
Mr Osborn took up professional windsurfing in 1992, soon after graduating from Yale University's business school, and had a respectable career on the world cup wave sport circuit, obtained a world ranking of 16, and opened a windsurfing shop.
But by 1996, he had had enough and, adopting the nickname Freebird, walked the Appalachian Trail.
He has since done that trail three times and has completed many others around the world.
Mr Osborn rates the Te Araroa Trail as tougher than any other he has done. He began shortly after the trail officially opened in December and expects to finish later this month.
He is not weighed down by GPS equipment and has never figured out how to use a cellphone.
Instead, he uses maps and leaves intentions as he goes.
Mr Osborn said he had chosen to relinquish his business and live below the poverty line.
There was also a spiritual aspect to his decision to travel and live lightly.
"It's just simpler and easier. It's a metaphor for life. What some people consider luxury items can be a burden," he said.
On his first long-distance tramp, he took a lightweight hammock, reasoning it would be lovely to relax in it at the end of each day.
After three weeks, he gave it away.
"It ended up being a dead weight in the pack. It ended up, literally and figuratively, a burden," he said.
