I have made my views clear about this on another forum, but I'll say that I agree with Kelby and Ane...

Indeed, great writers steal, but they do not steal whole characters and then make their own story about them. They steal images, words, scraps of sentences, style and the like, but they do not make stories with characters. I suppose that's more like borrowing actually... You use it for whatever mostly mediocre purpose you like, but ultimately that character will always stay the character of the original writer. No-one will ever credit a writer with making a character better then it was in its original version. Same as a film character is very rarely called better than its literary counterpart. Ultimately the writer who has used such a character has to give it back, which makes it rather borrowing than stealing.