Open source is fine, but it doesn't take a worldwide community to create a great operating system. Look at Ken Thompson creating Unix, Stephen Wolfram writing Mathematica in a summer, James Gosling in his office making Java.
Bill Joy ran the development team, Gossling worked for him... depending on who you talk too either Bill Joy or James Gossling is credited as the creator of Java. In many cases things of this nature are rarely one individual.
That being said... BOTH Joy and Gossling are noted technologists (from Sun Computing) and very WELL respected in the industry.
And more importantly what Joy has done in this article is given a solid referential indorsement to Apple's hardware and operating system. This is amazing given Sun's place in the industrial computing marketplace.