The bug (or how I understand it, which, again, could be wrong) is that that specific shader is mixing sampler2D and sampler3D uniforms, which is forbidden by the Opengl 3.3 shader spec.
The reason it works at all on NVidia cards is that apparently NVidia's shader compiler plays fast and loose with that part of the shader specification and allows mixing sampler2D and sampler3D elements, while ATI/AMD and Intel's shader compilers will fail to compile that shader.
Failure to compile the shader results in voxel quest only rendering the 'ocean' tiles, tree tiles (without lighting), and building tiles (again, without lighting), and everything else as background/sky gradient.
Someone committed a "fix" to one of the github trees which more or less patches out that shader or the offending part of it, but this just means it renders the wrong way on ALL cards, including NVidia ones.
Hopefully it will eventually be fixed properly in an opengl shader spec compliant way.