So, yeah, simple question, tricky answer. I'm not familiar with the Skyrim/Creation Kit EULA or how fits with IP laws (in any country), and though I doubt we've got anyone who is, I feel it's worth seeing if we can come up with a decent guess about it .

I would expect one could at least use it for art assets (models, textures, ect.), but I'm not 100% certain and there's a lot more to a mod than that.

For anyone not familiar with the http://creativecommons.org/licenses/ are a set of layer-approved licences which one can use to make clear how one's work is to be distributed and used -- whether people are free to do what they like as long as they credit you, or can share it but not make derivative works, or can do what they like as long as it isn't commercial, or... in short, what's cool and what's not.

EDIT: I'm also not sure this subforum is the perfect place for this thread, but I can't think of a better one .