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Date:         Tue, 1 Aug 2017 15:25:24 +0200
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From:         Frank Mittelbach <frank.mittelbach@LATEX-PROJECT.ORG>
Subject: Re: \usepackage problem with LaTeX 3
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Status: R

Am 31.07.17 um 16:45 schrieb Will Robertson:

>> To satisfy the LPPL I thought the right solution is to copy 
>> `fontspec.sty' to `fontspec-patched.sty', then applying the 
>> following change:
> 
> In fact, requiring a change to the filename is no longer written 
> explicitly into the LPPL. (Long story, don’t ever ask Frank how many 
> emails it involved.)

but you didn't listen carefully, did you? :-)

so let me repeat my usual sermon on that matter ...


it is true that name changes aren't any longer a 100% requirement but

  IN SITU CHANGES ARE STILL EVIL

and therefore not at all recommended, at least not in the TeX world 
where file names are part of the language and thus part of the 
communication that a language like LaTeX is trying to provide.

if there are several fontspecs out in the wild (and I'm not talking
about different releases of different age in non-updated distributions) then

  - CTAN can't properly handle that
  - distributions  can't properly handle that

  - which fontspec being found might be somewhat random

  - users may or may not be able to properly handle that

  - users will get documents that do not work even though their
installation has the latest fontspec (only not the secondary one used at
the other end)

  - documents will potentially come out differently despite the fact that
both parties think they have the latest releases

  - etc

Yes, in theory all can be traced back and in theory a \typeout or a
\ProvidesPackage mod is sufficient but on the whole it is bound to
produce tears

Whereas a package name change will clearly signal that something is
missing and if so what.

> You would be well within your rights to add something like the 
> following to the top of your patched version of fontspec.sty:
> 
> \typeout{This is Werner Lemberg’s altered copy of fontspec vX.X.}
> 
> The most important thing is that the altered code is clearly 
> differentiated to the user as being altered from its original.

no that's not really the most important thing. it is only the lowest 
common denominator where we
where able to meet after 1600 messages (here is the number :-)), ie the 
TeX world starting from Don's "change as you like
but call it something else" to the world of "freedom means I'm allowed
to do whatever I like; what do I care that this is a language in which
you try to communicate..."

So no, it is not recommended at all (at least not by me) even though it
is within the limits of the license.

In situ changes are only recommended in two cases

  - as owner/maintainer (or new maintainer, which is why LPPL has a
maintainer clause)

  - for local changes that are needed for some reasons (where one still 
should clearly identify with a \typeout or the like even if there is no 
intention to ever distribute)

but not for long-term or even midterm changes/extensions that are
intended to be distributed to more than a handful selected people.

The way I understand Werner his intention is beyond his own machines so
I think his approach of not changing fontspec without changing the name
is the right one.

His problems, however, are neither directly related to fontspec nor to 
LaTeX3 they are in fact more general ... discussion in separate message

cheers
frank