Re: Are lilypond output files subject to GPL?

[Jonas Hahnfeld]

Am Freitag, den 25.09.2020, 17:11 -0600 schrieb Carl Sorensen:
> After our two-day break as requested by Jean, I thought I'd look for
> something definitive about the question raised by Karsten.
> 
> I haven't found any cases where this question has been adjudicated, so we
> don't have the court's opinion on this.
> 
> However, the FSF has been active in defending Free Software, and created
> the GPL 3.0, the AGPL 3.0, and LGPL 3.0 in response to court cases and user
> behavior.  And I think you would be hard-pressed to find anybody who is
> stronger in terms of asserting "copyleft" than the FSF.
> 
> With that in mind, I find these the answers to these two questions in the
> FSF GPL 3.0 FAQ to be clear, convincing, and certain that there is no
> mechanism by which GPL 3.0 applied to LilyPond or OLL can result in GPL
> requirements for LilyPond output.
> 
> [...]
> 
> Is there some way that I can GPL the output people get from use of my
> program? For example, if my program is used to develop hardware designs,
> can I require that these designs must be free? (#GPLOutput
> <https://www.gnu.org/licenses/gpl-faq.en.html#GPLOutput>)
> 
> [...]
> 
> So the only way you have a say in the use of the output is if substantial
> parts of the output are copied (more or less) from text in your program.

AFAICT this is partially the case for the Postscript output, see the
files in ps/ and in particular music-drawing-routines.ps, maybe also
parts of scm/framework-ps.scm and scm/output-ps.scm. (The font is also
embedded, but has an explicit "Font exception" for that case.)


> Having this strong statement from the FSF, I feel no need to worry about
> losing my music to the GPL.  If anybody has case law where this principle
> is violated, I would be happy to hear it.

I think this addresses only part of the questions, namely the
implications for the output. The other topic is sharing code that uses
OLL, which is much less clear to me but IANAL. I would generally agree
that LilyPond input files can be considered some form of "programming",
but it's beyond my knowledge how GPL applies to functional languages
like Scheme where there is no binary form. The main question (for me)
is:

Does "\include"ing OLL make the .ly file a "covered work" that is based
on OLL?

As far as I understand, David K. expressed that merely calling the
functionality has no implications. Getting a definite source for this
would be great because I do see the potential concerns with this
question; after all it would be different from linking to library
compiled from, say, C code under the GPL.

Jonas

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