From the SRF02 datasheet:
The SCL and SDA lines should each have a pull-up resistor to +5v somewhere on the I2C bus. You only need one pair of resistors, not a pair for every module.
There are no hardware resistors on the Axon I2C bus, but you can activate pull-up resistors in software.
Here is an i2c.c snippet from AVRlib:
// set pull-up resistors on I2C bus pins
// TODO: should #ifdef these
sbi(PORTC, 0); // i2c SCL on ATmega163,323,16,32,etc
sbi(PORTC, 1); // i2c SDA on ATmega163,323,16,32,etc
sbi(PORTD, 0); // i2c SCL on ATmega128,64
sbi(PORTD, 1); // i2c SDA on ATmega128,64
On the Axon, SCL is D0, and SDA is D1.