"Keep it" in what way? You can save a copy of it to your hard drive, if that's what you mean. You can't go around pretending that you drew the characters. Whether or not you can reprint it in another medium is kind of a legal gray area that we're not really sure about. So far we haven't done so, and I think you should probably ask the original artists for permission if you wanted to do something like that.
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The what mentioned above is total fiction. Please don't take it seriously!