Arduino LLC and arduino.cc are the original group. Genuino is a new trademark intended to be more clear, but they have an uphill marketing battle, to say the least.

Arduino SRL and arduino.org are the former member who independently (and without knowledge of the group) registered the Arduino trademark in Italy. He then refused to transfer it to the group, and was pushed out.

The story gets worse from there. I'm not a fan of blacklists, but I make a point of clarifying the .cc vs .org distinction to whomever will listen.

.cc is Completely Correct.

- http://www.zdnet.com/article/whats-in-a-name-the-battle-for-...

- http://makezine.com/2015/03/19/massimo-banzi-fighting-for-ar...

- http://hackaday.com/2015/02/25/arduino-v-arduino/

edited to add:

- http://hackaday.com/2015/07/23/hackaday-interviews-federico-...