A guy called Fabien released a review of q3 source code. He has done reviews of other id games also, including quake and doom.

key points

Part 2 : New dualcore renderer with material based shaders (built over OpenGL Fixed Pipeline).
Part 3 : New Network model based on snapshots.
Part 4 : New Virtual Machines playing an essential part in the engine, combining Quake1
portability/security with Quake2 speed.
Part 5 : New Artificial Intelligence for the bots.

Read more @ http://fabiensanglard.net/quake3/index.php

Should be an interesting read.

(Edited 2012-07-02, 11:41)

I mailed him about ezquake and fodquake. Will be nice if he take's a look on them to and write articles about them

My review on the ezquake source code:

* omg this is a mess. :p

hehe

But it works

In contrast, fodquake source is a pleasure to play with, though it lacks many ez features

I think his blog is a lot of fluff an not enough "stuff"