Re: copyright issues and derivative work (the case of matlab-mode)

[Eli Zaretskii <eliz@gnu.org>]

> From: Uwe Brauer <oub@mat.ucm.es>
> Date: Tue, 23 Nov 2021 17:25:45 +0100
> 
>     3. Patches, that contain more than 15 lines, which according to
>        https://www.gnu.org/prep/maintain/html_node/Legally-Significant.html
>        is legally relevant. However the current HEAD (tip) state of the
>        repository contains less than 15 lines or even no line at all.
>        Now there are two possibilities.
> 
>        a. The orginal patch is no longer relevant, and therefore no action is needed.
>           That is what common sense would tell me.
> 
>        b. Although the code is not present now, it was present in some
>           commit in the past, therefore the rest of the commits is
>           derivative work.
> 
> If b. is the case we are doomed, but I cannot belive that some commit at
> some point acts like a virus «infecting» the descents of that commit,
> till today.

It's a, assuming that those code lines are gone for good, i.e. the
current code is not merely some transformation of those original
lines.  The "annotate" (or "blame") command will not tell you, because
it attributes whole lines; you need to look at the diffs between the
last version that did have that code and the current code, and analyze
that.

Btw, the "15-lines" rule is just an approximation: depending on what
are those lines, it could be much more, or it could be slightly less.
It's a judgment call, not a mechanistic line count.