Jose: you can use either the transistor logic-level translators, or the 4.7K pull-up resistors. The first option is the suggested way to do it, but I'm able to work with my MLX90614 BCI using the resistors.
Now the bad news. For me.
I put together the thermocam using an Arduino Leonardo, and tried to run the configuration sketch to improve the quality of the data received. Alas... when you reset the Leonardo, the serial port disappears... meaning that by the time I fired up TheraTerm to "talk" to the arduino the numbers you are supposed to save for later were already gone, and the sketch had already tried -and failed- to overwrite them. After that I added a long pause at the start of the app and was able to catch the full output from the program, but the writing of the registers kept failing. Now my MLX90614 is waaaay off (ice reports -253 celcius or so, skin 120 degrees or something to that tune). The ambient temperature seems to be accurate, but otherwise the sensor just went bonkers.
If there's anyone around here with a MLX90614ESF-BCI that could dump his/her EEPROM data and send it to me I would be extremely grateful. I rewrote the sketch to rewrite the EEPROM registers (now you have to actively request each register to be overwritten, by hand) and I added the option to dump the EEPROM and/or the RAM, so it's just a matter of loading a sketch, dumping the EEPROM and sending me the results. Please