How to test/connect the CAP-150 capacitive sensor
For "Load" connect a resistor of perhaps 1K from BLK to 5V. 5V to BRN, GND to BLU. 

Measure the voltage when 'Low' at the black wire with a voltmeter (to GND) - the guarantee of 2V is a bit close  to the maximum but I bet that with 1K the actual voltage will be more like 0.2 to 1V and it will work fine connected directly to the microcontroller input.

The 10mA comes from the power supply, not the Atmega, so no worries. 1K will draw an additional 5mA when low, again from the power supply.