Are you still looking for a library for max31865? I can made a preliminary library for max31865. I am in the process of finalizing it and will post it on Arduino Libraries section later in the month of July. It works with Arduino Due. Please note max31865 works on 3.3 V logic level. If you plan on interfacing max31865 with Arduino Uno, you will have to use a level shifter in between.
For library drop me an e-mail at firstname.lastname@example.org