I have a friend who has a moral objection to the casting of spells when it is done by player controlled characters. this person was looking forward to trying out Skyrim, but then learned that certain kind of spell must be cast to advance the main quest. I'm curious if there are any mods that remove this wrinkle so that my friend can have a nice time playing the game.

Thanks for your help!

If you're talking about shouts, then I don't believe there are any mods that change this. You have to cast the shout to progress through the main quest. Your friend could always just skip the main quest, it's pretty terrible anyway. He will be much better off never doing it. You can also use http://skyrim.nexusmods.com/mods/25404 mod and http://skyrim.nexusmods.com/mods/25204 mod to skip starting the main quest and not be the Dragonborn.

Another option is to use console commands to skip quest stages involving you to cast a shout. You can look on the http://www.uesp.net/wiki/Skyrim:Main_Quest to find the ID of the quests and how to skip stages of the quest (click on the quest that you want to skip parts of, and look below for the Quest Stages section).