Yellow/Orange Fungus on Oak Tree
I can't say for sure but it looks like a species of the Laetiporus mushrooms. Please refer to its wikipedia page for the full info. 

edit: I did not read your question fully and now I see that you reached the same conclusion. Just ignore my answer. As to the second part of your question asking if it could be anything else, that is quite hard to visually determine as there are many look alikes in the mushroom kingdom. Read this for some imposters.