Re: [Fwd: Re: I-D for the PATCH method]

Joe Feise writes:
> diff predates the FSF and GNU by a large margin.
> A quick search shows that the algorithm was implemented in the  
> early 1970s and
> described by James Hunt and Doug McIlroy in 1976 in a Bell Labs  
> tech report:
> http://www.cs.dartmouth.edu/~doug/diff.ps
> Bibtex reference (http://www.cs.dartmouth.edu/~doug/doug.bib):
> @techreport{McIlroy76b,
>    author = {J. W. Hunt and M. D. McIlroy},
>    title = {An Algorithm for Differential File Comparison},
>    institution = {Bell Laboratories},
>    address = {Murray Hill, NJ},
>    number = {CSTR 41},
>    year = {1976}
> }
>
> It is my understanding that what is now called "normal diff" was  
> the original
> implementation's output. Context and unified outputs were added later.

This is my understanding of this technical report as well.

While IANAL, even if there had been a patent filed on this technology  
in the mid-70's (and I'm pretty sure there was not), it would now be  
expired, since you have a year from public disclosure to file, and  
patent durations are 20 years from filing.

So, at least for normal diff, we have both a stable reference, as  
well as a pretty clear story on freedom from intellectual property  
restrictions.

- Jim