LEGO EV3 I2C Compatibility
LEGO doesn't really follow I2C standards, so "close enough" is a good description.

The EV3 hardware developer kit (available for download at http://mindstorms.lego.com) has this to say:


  4.1 I2C communication
  
  The EV3 platform supports the same level of I2C communication as MINDSTORMS NXT. This means that
  system support a maximum of 9600 bit/s and maximum 32 bytes communication buffers. All I2C
  communication is running within software drivers. External devices are required to include pull-up
  resistors on both pin 5 and 6 on 82K ohm. If multiple sensors are used on the same bus the total
  impedance needs to be adjusted accordingly.


Most off-the-shelf I2C devices use 10k pullup resistors (although it looks like it might be 4.7k in your case). These must be removed and replaced with 82k resistors to be compatible with MINDSTORMS.