I don't mean to be negative, like the guys friends that laughed at the project - but coding an MMO is several orders of magnitude more complex than putting together an Octree renderer.
Best of luck with it, but, so far, nothing to see here.
However, I'm also cheesed at the misuse of the term MMO, Minecraft is pretty close but the lack of a centralized game world in any way makes it unlike most MMOs, and by extension doesn't really fit the term. It is merely a persistent multiplayer construction set. N8 (Neverdaunt) or Wurm Online (which notch had formerly worked on), for example, are similar construction-oriented games that definitely fit the MMO moniker because there /is/ a centralized persistent game world. Dealing with the side effects of such a architecture does make things an order of magnitude more complicated.
An Octree is just one technique to reduce the size of the Potentially Visible Set of geometry that is sent to the rendering pipeline. While its a quite a natural fit for a voxel-style world, such as minecraft, there are many techniques to achieve this; an octree just being one.
If the Octree was the core technical challenge and data structure used to create every MMO, then I'd have no issue with the article. But its really not - its a simple technique, graphics 101, used to speed up rendering (or collision detection).
Further, just having an octree is not nearly sufficient for handling MMO scale issues - a lot more needs to go into structuring the world - when those larger challenges are solved, I'd like to read his article on it.
If I see an article about coding an MMO I expect to read about the complexities of scale and persistence, and supporting a consistent gameworld for a lot of players - these are the main challenges unique to an MMO.