Okay - this is my own personal views on things.
I personally think if I buy something, it is mine to do what I want with it afterwards. However, there are some fine lines. I can't rewrite Goblet of Fire, for example, and sell it as my own [ well, word for word, or even mostly the same words ] . However, I could sell my copy of the book once I was done reading it.
Unfortunately, software, and some other industries, have tried to curtail this.
Now, how does this relate to The Sims2 and CC? Well let me tell you....
*that was supposed to make you laugh - so laugh - have some rum-corn*
Basically, you can't make money using what is mostly their code - that's plagerism, just like re-writing a novel someone else did first. And unfortunately, while the artwork in CC is done by players, and code tweaks and such are done by players, there is still a sufficient quantity of the original in 99% of all CC that it still belongs to EA for purposes of intellectual property rights.
The problem is, too many folks see the new mesh, new functions, and new textures and forget the rest of the stuff lying beneath the surface, like an iceburg.
And interestingly enough, the stuff that has perhaps the least amount of the original code seems to all be free