A very sad and really disturbing conflict in the Arduino community.
One little fact (need to be confirmed, but I believe it’s true):
“Smart Projects had been paying royalty fees to Arduino LLC until recently”.

That’s dead simple then to me:
Arduino LLC is the righteous owner of the trademark, and until recently “Smart Projects” has recognized this fact (and paid the royalty). But they have become more greedy, I suppose…

The article also indicates that Arduino LLC trademarked the name in the U.S. in 2009, and that Smart Projects had been paying royalty fees to Arduino LLC until recently. Those additional facts seem to suggest that until recently, Smart Projects considered LLC to be a rightful holder of the trademark. Why did their theory change?

via Arduino Dispute Reaches Out To Distributors – Slashdot.