There are at least three legal rights that bear on the question of whether or not someone can make commercial use of an existing quote or song lyric. These are Copyright, Trademark and the Right of Publicity.
With respect to Copyright, let’s first clarify that words, phrases and titles are not by themselves copyrightable. See: http://www.copyright.gov/circs/circ34.pdf.
However, when the words or phrases you want to use are contained in a larger, copyrighted work, then they are indeed protected by copyright. The same rule applies if the phrase you want to use is a quote, whether from a copyrighted speech or a catchy aphorism used by a writer or one of her characters in the course of dialogue. Use of the same content in your commercial product without the permission of the copyright holder, whether in a greeting card, or other paper product, is an infringement. The Copyright Office addresses the same question in one of its own FAQs: http://www.copyright.gov/help/faq/faq-fairuse.html
“If you use a copyrighted work without authorization, the owner may be entitled to bring an infringement action against you. There are circumstances under the fair use doctrine where a quote or a sample may be used without permission. However, in cases of doubt, the Copyright Office recommends that permission be obtained.”
Then the question is whether or not the a person's particular use is defensible as a “Fair Use." Consider the four part Fair Use test:
- The purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
- The nature of the copyrighted work;
- The amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
- The effect of the use upon the potential market for or value of the copyrighted work.
When considering whether or not pithy sayings might be protectable on their own, consider the case of Ashleigh Brilliant (http://www.ashleighbrilliant.com/), who has successfully defended his copyright of his collection of original sayings. Historically, certain quotable essayists and humorists have sent out ‘cease and desist’ letters to stop the use of their quotes. However, given how broadly some of these materials are now disseminated online, it is becoming increasingly difficult for rightsholders to stop commercial use.
As for trademark, if the quote or lyric you want to use is being utilized as a trade or service mark then your use could cause someone to believe that the trademark holder is the source of goods on which you use it. That is the gravamen of trademark Law – to avoid just such confusion as to origin. You will want to make sure that you are not using a pre-existing catchy saying associated with another company to attract prospective purchasers of your goods. Many such phrases, such as “Show Me the Money,” “ET Phone Home,” “Got Milk” and “Just Do It,” are trademarked, and cannot be used by you without likely objections, if not claims, by their owners.
Finally, if you are using a quote, and in conjunction with the quote you use the author’s name, that is a use that can easily been seen as a violation of that person’s Right of Publicity, even if it is just being used to identify the source of her quote! What if you were to use the quote without the author’s name? Would that diminish sales of your product? If so, then clearly there is a commercial advantage to using the name. At the same time, if you go to the author or her agent or publisher for permission to use the quote, it is very likely that the permission will come with the condition that the quote be attributed. And that is a large part of the reason a royalty payable on your sales will likely be required in exchange.