Like Google Adwords does Yahoo PPC network also restricts copyright and trademarked words from being put in the Ad?
I believe they do, but maybe it's just the keywords they restrict. If I remember correctly a while ago I tried to place some ads, but some of the keywords were deleted for that reason, but sorry, I cant remember if the ads were as well or not.
Here's a good rule of thumb: whatever Google does, the other search engines do too. Of course, the way to find out if Yahoo has the same rule is just to try it. If they object, they'll tell you. But I think you can avoid the hassle by finding out first. Google has their Adwords policies and guidelines. The others have their own versions as well.