Map Updater/Map Loader only works with Windows. There's a version of Map Loader that works with some Mac OSX flavours, and that's where support for non-WIndows users ends.
Of course you could make a Map Updater for all current Mac OS versions, and make a Linux version. But:
1) Why not make a Map Update method that works straight from any browser without need to install anything on your computer?
2) Why not make a Symbian version?
It can be done. Downloading maps and unzipping them to the right folder is really a very asy task that doesn't require the hundreds of megabytes of Map Loader/Updater and .NET framework. http://nokiamaps.site666.info lets anyone download maps for Nokia Maps 1 and 2 (but not yet for 3) so you can unzip them into the maps folder on your phone. Works on all operating systems and there's no need to install anything, so you can even do it in hotels, schools, internet cafes, and other places where you can't install .NET and maploader or map updater.
Symbian already has a web browser. New Nokias have a zip manager built in. So feeding maps to your memory card could easily be done without a computer and tons of megabytes of code.
So why not add a Symbian map loader that can 1) download and install maps straight from your phone, and 2) unzip maps downloaded from a standard computer web browser into the right folders? It doesn't take much more than a bit of code to tell the browser and zip manager what to do, so it could be included in the Nokia Maps program itself.