Ask Slashdot: Using Code With an Expired Patent?

kruhft writes "I was recently doing some research into Genetic Programming and found a library through a blog post that looks to be useful. After looking over the code and license, I found that this was the first piece of code I had seen that was protected by a patent, issued on June 19, 1990. I read that patents last for 20 years, meaning that the patent that this code refers to is expired. Is there any way for me to be sure that using this code is safe from any patent troll attacks if I choose to use it? Would rewriting the code keep me from violating any other patents that the author might have regarding the use of such an algorithm? Does the code pass into the public domain after the patent expires?" Note to Chrome users: the above link ("a library") works for me in Firefox, but not in Chrome on Linux; YMMV.