PS: I have translated to Squeak the C code to generate random numbers with a normal distribution published in "Numerical Recipes in > C", second edition, and implemented the class NormalRandom. Is it legal > to publish such code?
As a lawyer, I can offer a definitive answer: It depends. :-)
In practice, I seem to recall that Numerical Recipes had a specific license set forth somewhere in the preamble or at the end of the book, stating how and for what you can use the code; which as I recall was a liberal license. I would start there, and if it lets you do what you want, you're all set.
In the alternative, just ask the authors for their OK. (Consent is the single best defense there is to a copyright action.) Saul Teulkowsky and his wife, Roslyn, are old bridge teammates of mine, so I'd be pleased to make an introduction.
Otherwise, we get into tricky questions of fair use, which while it doesn't ordinarily get in the way of taking a code snippet from a book, the answer I'd have to give as a lawyer is, "it depends."