If the copyright of the material is at all in question, we recommend that you do not use it in your designs. Better safe than sorry!
Very short phrases or quotations can sometimes be ok if the quote is old enough to fall into public domain (for instance, a Benjamin Franklin quote). To be doubly safe, you should credit the original source within your design. Please use your best judgement and whenever possible, try to avoid any potentially copyrighted material.
If the material is not clearly in the public domain, we will most likely not be able to accept it. Generally, song lyrics can't be used without direct permission from the copyright holder, even if a citation is given.
We require that submitted designs do not contain any trademarks, logos, or copyrighted material that may be subject to any infringement or intellectual property concerns. Unfortunately, we are not able to advise on a case by case basis whether a design is compliant with our requirements. We recommend reviewing the public domain, copyrights, trademarks, or patents for any quote or lyric that you would like to use in your design before including it in your submission.
Check out our "Sound Advice for Ensuring Your Work is Original" article for more tips.