Hi dt,
Hope you are doing well. That SW is used for the NTAG I2C plus Explorer Kit, with the LPC11U37H. The lpc8xx code is not updated, as it is not used in this Kit. The configuration of the project is that those files even compile.
You can use the same structure of the functions, but in this case you would need to adapt the I2C functions.
Other option is to use the NTAG I2C plus example from the SDK. Some of our boards have the implementation of the example (for example the FRDM-K64F or the LPCXpresso55S69).
You could download it from this page: SDK Builder.
In MCUXpresso you will be able to import the ntag_i2c_plus examples. 
These examples would be helpful to port to other MCU.
Best Regards,
Ricardo