There's a growing trend for authors of IE mods to state that another IE mod is 'required' or 'must be installed', when the reality is that their mod simply hasn't been tested without that other mod installed. What they should in fact say is something along the lines of "this mod was made with Baldurdash installed, and has not been tested on a non-Baldurdash installation. We therefore recommend that you install Baldurdash prior to installing our mod. However, since we cannot say for certain that our mod will not work on a non-Baldurdash game, there is a chance that it will be fine without it. While we will not provide technical support to players running our mod on a non-Baldurdash installation and have no plans to alter our mod to make it compatible if it not, we are interested in learning whether or not it works - so please, let us know!"
EDIT: If, on the other hand, an author knows 100% for certain that their mod requires the installation of another, he or she should clearly state the precise reason(s) why this is the case in the mod's readme.