I have seen some pretty sorry examples of what people call MEL tutorials . . . . some of the clowns that write these obviously never even bother to test their code. Kind of like when you were in school and you find out that the answer in the math book is wrong . . . very frustrating, and certainly not helpful.
There is really not a lot of variation of MEL from one version of Maya to the next. If there is, it is usually only added functionality, and added functionality should not cause problems, unless you run code meant for Maya 7 in Maya 5, then you might run in to some issues.
"The Sage as an Astronomer: If you still see the stars as something above you, you lack the eye of knowledge." Friedrich Nietzsche