Since bitcoin isn't a company that might sue me for copyright or trademark, can I sell items with the bitcoin logo on them? Same goes for all the others like Ethereum, litecoin, etc. Does the fact that these are decentralized allow me to sell stuff using those names?
I am releasing a product soon where I had to research this as well.
It comes down to what the license the image(s) were released under, if they were created by a company.
While Bitcoin, Litecoin and various others have not had their logos copyrighted, as no one has legal authority to claim ownership of such images.
Ethereum and Dash have released their logos under various Creative Commons licenses. All of which allow you to:
"Share — copy and redistribute the material in any medium or format
Adapt — remix, transform, and build upon the material
for any purpose, even commercially."
According to the CC website:
https://creativecommons.org/licenses/by/3.0/
