It's either the genuine article or a very good forgery. I haven't read the whole thing yet, but it's written by a nineteen-year-old Li Kao, and Number Ten Ox is only a bit character, an assistant to Chang Heng, who is (as in the original) long dead.
It's definitely a first draft. If you haven't read the original, I don't recommend reading it. Read the published version first. But if you have, this is an excellent way to get some insight into (what appears to be) Barry Hughart's writing process. And there's not only stuff that went into his later books, there's also stuff that never made it into any of his books.
Here it is. Enjoy.