The pull-up resistors mounted on the DUE's pcb are actually 1000 ohms, not the 1.5k shown on the schematic (at least they are 1k on my DUE's).
In any case, both values are unnecessarily low, undoubtedly causing many DUE boards to be needlessly cooked. This can happen simply by attaching an external I2C bus (that may have additional pull-ups installed).
I recommend that the on-board pull-ups be removed (there are no side-effects), and use your own external pull-ups.
For one of the better run-throughs on how to size I2C pull-ups see:http://www.edn.com/design/analog/4371297/Design-calculations-for-robust-I2C-communications
What K3FY is doing is fine (pulling up the I2C lines to 3.3v). It will work as long as the threshold voltages for valid 0's and 1's on his Max board work around the 3 volt range (one would need to read the specs of the MAX board interface to be sure).
The I2C bus is an open-collector bus. So, the end-user is responsible for deciding what voltage to pull the bus up to, and what values to set the pull-up resistors. Often times this is a tradeoff between threshold voltages, bus capacitance, clock speed, and power consumption.