Here’s a brilliant post by designer Emily McDowell on copyright and fair use: Using Famous Quotes On Products: When Is It OK?
A few salient quotes:
[Works] published before 1923 are in the public domain and are therefore legal to use.
[Attributing] a quote to its author does not make it legal to use the quote.
And, my favorite:
In fact, when I started to feel really boxed in creatively by being limited to using pre-1923 quotes, I started writing and selling my own stuff, which is what led to my card line and was the smartest thing I could have done!
Emily also includes a couple of links to legal articles for further explanation, so be sure to check out her complete article.
Merch & Etsy Sellers take note! ☺️