No problem. It appears the anfis function is written in MATLAB itself, and not compiled. If it was compiled code, then no, they do not give it out, and the only way to see the code it to work for TMW. But, since it is written in MATLAB, then you can read the code directly. As such, there is no better source than to read the code yourself. That IS the original code.
If it is too "vague" (I'm not totally sure what vague means here to you) for you, we cannot help, beyond teaching you a detailed course in the subject. For example, perhaps you do not understand why the author made some specific choices in writing the code. That detailed course would be wildly beyond the scope of Answers.
So spend the time reading the code in detail, because that really is the code.