Why doesn't the Micro OLED library compile on my DUE? I have an Arduino DUE and just got a Micro OLED display from SparkFun.

Using their library, when I try to compile I get the error below.  Other example code works just fine and I've programmed this thing a million times with my code.  So it's clearly in the SparkFun code.

Here is the SparkFun tutorial page with a description of the product:

https://learn.sparkfun.com/tutorials/micro-oled-breakout-hookup-guide?_ga=1.19136059.2055231411.1404437767

Here is the library I am using:

https://github.com/sparkfun/Micro_OLED_Breakout/tree/master/Firmware/Arduino/libraries/SFE_MicroOLED

Here is the error I get:

Build options changed, rebuilding all

/Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp: In member function 'void MicroOLED::spiSetup()':

/Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:46:10: error: cannot convert 'RwReg* {aka volatile long unsigned int*}' to 'volatile uint8_t* {aka volatile unsigned char*}' in assignment
    ssport  = portOutputRegister(digitalPinToPort(csPin));
            ^
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:48:51: error: 'portModeRegister' was not declared in this scope
    ssreg  = portModeRegister(digitalPinToPort(csPin));
                                                     ^
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp: In member function 'void MicroOLED::i2cSetup()':
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:84:2: error: 'TWBR' was not declared in this scope
    TWBR = ((F_CPU / I2C_FREQ) - 16) / 2;
    ^
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp: In member function 'void MicroOLED::parallelSetup()':
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:109:10: error: cannot convert 'RwReg* {aka volatile long unsigned int*}' to 'volatile uint8_t* {aka volatile unsigned char*}' in assignment
    ssport  = portOutputRegister(digitalPinToPort(csPin));
            ^
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:111:51: error: 'portModeRegister' was not declared in this scope
    ssreg  = portModeRegister(digitalPinToPort(csPin));
                                                     ^
  /Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:114:10: error: cannot convert 'RwReg* {aka volatile long unsigned int*}' to 'volatile uint8_t* {aka volatile unsigned char*}' in assignment
    wrport  = portOutputRegister(digitalPinToPort(wrPin));
            ^

/Applications/Arduino.app/Contents/Resources/Java/libraries/SFE_MicroOLED/hardware.cpp:119:10: error: cannot convert 'RwReg* {aka volatile long unsigned int*}' to 'volatile uint8_t* {aka volatile unsigned char*}' in assignment
    rdport  = portOutputRegister(digitalPinToPort(rdPin));
            ^
  Error compiling.
That library is uses some AVR specific methods, that aren't implemented for the ARM processor in the Due. 

I don't see a real easy way to port those methods.