

Ask HN: Using Code after Patent Has Expired - kruhft

I was recently doing some research into Genetic Programming and found a library (ftp://cs.ucl.ac.uk/genetic/ftp.io.com/code/koza-book-gp-implementation.lisp) through a blog post (http://bc.tech.coop/blog/040619.html) 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 (http://www.ptodirect.com/Results/Patents?query=PN/4935877), 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?<p>Sorry about the inline URLs; I'm not sure how I put actual links in my posting.
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mark-r
Even if the patent has expired, copyright is still in place. You can't use the
code unless it was placed in the public domain by the author or you have been
granted a license. You could however write your own code that expresses the
same algorithm. Nothing about this protects you from violating any other
patents.

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kruhft
But since the patent has been done and expired, the actual algorithm is no
longer patentable again, right?

~~~
mark-r
The patent may be expired, but an enhancement to it might be granted a new
patent, and your implementation might inadvertently infringe on the
enhancement. There may also be cases where two patents cover the same
algorithm. Be careful about assuming a patent has expired, terms have changed
in the past and you have to consider foreign patents as well.

