Hello, I was just thinking about the EULA for the CS and how it stakes claim to copyright for Bethesda Softworks over your mod.

Now, does this mean that if you create a mod *without* use of the Construction Set provided by Bethesda Softworks (thus not agreeing to the EULA), do you still surrender ownership of the mod? I know that creating resources through other tools (such as Blender for models, Gimp for textures, etc) allows you to keep copyright of those resources, but does the same apply for a third party editor?

Like I said in the title, this is just out of curiosity. I have no intent (or interest ) of getting into a dispute with Bethesda over copyright claims regarding anything.

I personally think you wouldn't, I'm not a lawyer though. But either way it would be difficult to prove you didn't use the CS since the format of the esp would have to be the same for Morrowind to use it.

My guess would be that any file you distribute for use in the game would fall under the same EULA, regardless of using the CS or not. This is why using files from other games is frowned upon. Although something you make in Blender or Gimp is clearly yours, and I doubt Bethesda would ever contest that.
It's not something you should be worried about though. It's probably some confusing legal matter that the lawyers came up with, and I have never heard of Bethesda claiming ownership over any mod of any sort.
The whole copyright thing could even be there to protect us (the modding community) from people that might steal our work for use in other games.

That is probably part of it. We have already seen shady companies trying to re-package mods and sell them for profit, without the mod authors permission. It can also open up a slippery slope where someone could make a total conversion or a create an entirely new game from a mod and then try to sell that. It also makes sense as without Bethesda's creation of the game and it's resources, then there would be nothing to mod to begin with.

The sad irony of these posts is that those of us with legal experience can't respond to them without risk of engaging in the unauthorized practice of law (if you're not in the jurisdiction I'm licensed in) and/or creating some type of attorney-client relationship