Well they can copy all they want... Its when they take full credit or start selling it that it becomes illegal. Like lets say I was a professional artist (I'm absolutely not, this is just an example) and I saw some of her paintings and went: "Oh those look great! I want to see if I can make that as well!" So then I make them and just keep them. If people ask about the paintings I say that someone on etsy inspired me to paint this when I saw their work.you dont want people copying your drawings after all your hard work
But if I respond with "Oh that's my newest painting. Thanks for the compliment" its like I would be taking full credit... And if you sell it... Well your screwed then