Well, we have to thank you (tim and time again). Without you - SteinerX - we wouldn't have all the team members we enjoy to have now! And your work is becoming better and better all the way.
As for the Ambient Occlusion - this is an effect you normally get from Global Illumination (at much higher cost)
Global illumination is a lightning model using radiosity where light is coming from all directions. This creates the effect that parts of the model that touch other parts are made darker because of the diffusion of light (damn english, sometimes my knowledge of english is not enough to explain complex concepts... sham on me)
For a much better explanation see http://en.wikipedia.org/wiki/Ambient_occlusion
bakeing ambient occlusion into a texture can be done by most professional software packages but is very time consuming. In this case I used a base texture size of 4096x4096 with 2x supersampling which equates to 4 times the texture size. It calculates the ambient occlusion but instead of applying it to the model it saves it as BlackWhite value in a texture.
Partially my mistake... for some non important part, i have not take care of flip the UV piece... since AO is related to light, normal and polygones shadowing each other, i will be more carefull in my next model... i am pretty sure that you have know problem with the AO on the main boy, specially part where are the "rib"...
Well, in some cases we could have done better, but since the ribs for example touch the upper surface (the main body) at different points on their y-axis I cannot use AO on them, so I had to drag them off the uv map to not create undesired effects. We could only remedy this situation at the modelling stage and only with very difficult methods, or do not optimise the ribs at all in the uv.
ps: I answered you in the linked thread. Glad to hear and we will wait patiently for your return!