Dear 100 Hour Board,
I made an off-the-cuff t-shirt design that I've been told is good enough that I could think about selling it somewhere like RedBubble. Unfortunately, as I've been doing my homework, I've discovered several similar designs, including this nearly identical one. Would I violate copyright by selling mine?
I can find lots online about selling work inspired by others, but not anything about work you totally came up with yourself that you later discover is similar to others' (probably because it's so dead simple).
We here at the board are not lawyers; which means we cannot offer legal advice. For actual legal advice you should talk to a lawyer. It seems like your concern is a question of substantial similarity, which is whether your work is close enough to be prosecuted for copyright infringement. I skimmed over the Wikipedia article on substantial similarity and it does a pretty good job of explaining things. For more in depth research it has plenty of links to follow. I hope this was helpful. If you're really worried you could possibly change up your design a bit so that it's definitely unique. This isn't legal advice, but it's just a thought to consider. Good luck.