What he is saying is this
If you experience problems with pin-sharing you can move the DS3231/DS3232 SDA and SCL pins to any available pins on your development board. This library will in this case fall back to a software-based, TWI-/I2C-like protocol which will require exclusive access to the pins used.
That is if you have issues by sharing SDA / SCL (the wire protocol is meant to be shared between multiple devices) then you can use his library with non SDA/SCL pins of your hardware and his library will handle that OK so that the rest of your wire needs works fine