One is a point of sale peripheral, the other is a Linux desktop environment. Okay, they're both 'technology', but that category is huge and getting broader every year. In any case, neither product is widely known, it's highly unlikely anyone would confuse one with the other, or that it would hurt either brand if they did. The case for trademark infringement is practically nonexistent.
That said, I'm glad Groupon is changing it; the Gnome has rubbed me the wrong way ever since it was announced. The name isn't reassuring on a device meant for handling financial transactions, the early prototypes were a bit too 'friendly' and OLPC-inspired, the current one is huge and clunky, and it lacks support for newer technologies like EMV and NFC. Hopefully this will send them back to the drawing board. Thanks, nerd rage! You saved the day again.