Disclaimer: I'm no lawyer, I do not work for deviantArt, I'm merely someone who has been doing photomanips for quite a while and has taken the time to read quite a few articles on the topic. The views expressed hereunder are mine alone. They do not reflect any "official dA opinion" nor are they to be taken as "legal advice". Furthermore, you may live in a country that hasn't signed any of the treaties that govern international copyright law, so you'd have to check with your country's national laws.
I strongly urge you to not only read the journal, but also the comments underneath it as there are a lot more examples of what you can and can't