But though he is prone to give considered thought to a question before venting, McMillan is not one of those dreamy philosopher types. He's an extremely intelligent, pragmatic soul, who has knocked around enough not to fear an encounter with the media. In fact, he's even dabbled in things in that field - but more of that later.
At the forthcoming Australian national Linux conference (LCA 2010), which is to be held in Wellington from January 17 to 23, McMillan is literally playing the role of banker - he is managing the sponsors.
McMillan was born and raised in Rotorua, a city in New Zealand that is famous for its geysers - and also the smell of rotten eggs, the latter due to the geothermal activity that releases sulphur fumes into the atmosphere. Rotorua is also known for being home to the Waiariki Institute of Technology, the largest such tertiary institute outside of the main cities in New Zealand, so McMillan's venturing in that direction is not surprising at all.
After spending six years as an electronics technician, McMillan entered the field of computing. He has done it all in this field. "I've worked as a programmer, analyst, project manager, systems administrator, operations manager, pre-sales support, technical services manager, etc, etc, etc - pretty much everything from dogsbody to director, inclusive," he told iTWire in an interview.
McMillan is best known for being involved in setting up New Zealand's biggest open source company, Catalyst, in 1997. He recently retired after 11 years of working for the company. He's also been a developer with the Debian GNU/Linux project since 2002. Whether by accident or design, the last six digits of his mobile number spell out DEBIAN.
His experience with free software goes back to the early 1980s, the time when another bearded individual, Richard Stallman, was starting to put in place the foundations that have led to this genre of software becoming what it is today.
"I've done both (free and proprietary software), but free software is where I started, back in the early '80s when 'software' was a listing from a book or a magazine. I then moved to proprietary software where the source code was supplied to all the clients and nobody really specified any licensing," he said.
"In the early '90s I got involved in the bulletin board 'scene' in New Zealand and my interest in Linux grew out of that. When I was involved in setting up Catalyst IT in 1997 I was already actively using and recommending Linux."
McMillan switched to running early incantations of GNU/Linux on his laptop in the early '90s and has never looked back. There was no major or minor influence which pushed him in this direction: "It just came pretty naturally to me."
His first involvement with the LCA was in 2006 when the conference was held in Dunedin, the first time it was hosted in New Zealand. "Since it (LCA) was in New Zealand it was pretty much a no-brainer to attend, and I dragged along 11 other staff from Catalyst as well, since open source had become such a core element of our business by then," McMillan recalls.
"That was such a fantastic experience I've been to Sydney, Melbourne and Hobart subsequently, and dragged my wife and children along to the partners' programme too."