Almost everyone has heard of RetroPie.
The open source software which has enabled a bunch of Ikea tables with embedded Raspberry Pi.
Unfortunately, they've recently learnt a bitter lesson in trademarks, that unless you get there first, someone else can pull the rug out from under your feet, as the makers behind RetroPie call out for legal help.
Furthermore, they're practically claiming RetroPie as their own, as they have filed a trademark in America (yes, even though they're from India) to lay claim to 'RetroPie' and 'Emulation Station'.
Allegedly the person behind this trademark registration has come out with his side of events and reasoning why they've done this:
So perhaps a word of warning, even if you're creating something open source, even if you're giving it out there and believe the GPL and licensing protect you, ultimately you cannot stop someone unless you've put measures in place to protect it first, and you're able to chase after them with the money necessary to hire lawyers/solicitors. A sour lesson, all the same.