I figured this issue would be of interest to people on E2 since we're noding plenty of recipes, and I wasn't sure quite how copyright applied to them. The following was found on the web, on a United States Government web site, concerning copyright of recipes.
This is in response to your inquiry regarding the copyright registration of recipes. Mere listings of ingredients as in recipes, formulas, compounds or prescriptions are not subject to copyright protection. However, where a recipe or formula is accompanied by substantial literary expression in the form of an explanation or directions, or when there is a combination of recipes, as in a cookbook, there may be a basis for copyright protection.

Protection under the copyright law (title 17 of the United States Code, section 102) extends only to "original works of authorship" that are fixed in a tangible form (a copy). "Original" means merely that the author produced the work by his own intellectual effort, as distinguished from copying an existing work. Copyright protection may extend to a description, explanation, or illustration, assuming that the requirements of the copyright law are met.

To register the directions or instructions of a recipe or cookbook, send the following three elements in the same envelope or package to

The Library of Congress
Copyright Office
101 Independence Avenue
S.E.
Washington, D.C. 20559-6000

  1. A completed application Form TX;

  2. A nonrefundable filing fee of $30;

  3. A nonreturnable deposit of the work. The deposit requirements depend on whether the work has been published at the time of registration:

    • If the work is unpublished, one complete copy.

    • If the work was first published in the United States on or after January 1, 1978, two complete copies of the best edition.

    • If the work was first published in the United States before January 1, 1978, two complete copies as first published.

    • If the work was first published outside of the United States, one complete copy of the work as first published.

    • If the work is a contribution to a collective work, and published after January 1, 1978, one complete copy of the best edition of the collective work or a photocopy of the contribution itself as it was published in the collective work.
Copyright protects only the particular manner of an author's expression in literary, artistic, or musical form. Copyright protection does not extend to names, titles, short phrases, ideas, systems or methods.

Sincerely yours,

Register of Copyrights

What does this mean? Well, it means that the ingredients and method for cooking a dish, as listed in the recipe, cannot be copyrighted. However, the exact text used to explain the directions as to making the dish can be copyrighted, assuming there is enough there to count as intellectual effort. (For example, the instructions "mix well and serve immediately" surely could not and would not be copyrighted - but five paragraphs detailing preparation could be)

However, if the method of preparation was completely re-written by someone, it doesn't seem to matter if it describes the same method, or an altered method, it's not a copyright violation.

As to how this applies to E2 - it seems that it's not a problem to take a recipe from a cookbook, as long as the directions are substantially altered, especially if there are additions or deletions from the original text, since only the exact text in the original source would be covered by copyright.

I would say that if you are going to do a writeup to a recipe from a book/website/other source, you may want to credit the source for the original recipe, as it's just a good idea, and gives credit where credit is due.

Source:
http://www.loc.gov/copyright/fls/fl122.pdf