no real multitexture support for opengl. that is a must, if you want to
work with shader languages like glsl.

Multitexturing works fine. The only drawback is that only texcoords from the texture unit in the chain with the shader can be used. This only presents a problem if the texture dimensions are different sizes.

this should be easily fixed by someone with sufficiant knowledge of the
opengl world and gem (and time and resources...).

Unfortunately it is either not easy to fix or just beyond my abilities to do so. I have spent many, many hours trying to get this to work but cannot make it so.