Why there are only headers? Where can i download full code (cpp files) ?
The source files should be right under the "source" folder after you extract the zip. 1.03 is an old version though (I must have forgot to update this thread's download links), so maybe if you try again it will work. CVS is another way to get all the source, with the added benefit of getting the latest version (with all the bug fixes and new features).
Maybe we should add an option for the user to specify the location where impostor images must be saved/loaded from.
True, though it's usually just as easy to just move them from the bin folder into whatever media folders you want. The impostor autogeneration is meant more to be a convenience tool than an actual game engine feature that's used by the end user, but I guess it wouldn't hurt.
Another question about materials used for batches. It looks like material of entities is changed (internal shaders are applied). This means that I can not apply my material to the objects. How should I treat materials for batched entities?
The batch system does make a clone of your material internally to apply it's vertex shader, but that shouldn't matter because you can't change the materials of a batch after it's created anyway. What you do need to know about using custom materials on trees is this: If you use your own vertex shader, you'll need to manually integrate BatchPage's fade transition shader code into your own shader, since your shader will override PagedGeometry, and there's unfortunately no magical solution to combining shaders.
Also, keep in mind a little issue I've found: multitexturing with BatchPage using one set of UVs doesn't work correctly unless you write a pixel shader due to some issue with DirectX/Ogre and using a vertex shader without a pixel shader (and BatchPage has to use a vertex shader for fade transitions).