Re: LilyPond, LilyPond snippets and the GPL

[Hans Åberg]

> On 30 Oct 2019, at 18:48, Carl Sorensen <address@hidden> wrote:
> 
>> In general this is legally impossible; copyright law does not give you any 
>> say in the use of the output people make from their data using your program. 
>> If the user uses your program to enter or convert her own data, the 
>> copyright on the output belongs to her, not you. More generally, when a 
>> program translates its input into some other form, the copyright status of 
>> the output inherits that of the input it was generated from.
>> 
>> 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. For 
>> instance, part of the output of Bison (see above) would be covered by the 
>> GNU GPL, if we had not made an exception in this specific case.
>> 
>> You could artificially make a program copy certain text into its output even 
>> if there is no technical reason to do so. But if that copied text serves no 
>> practical purpose, the user could simply delete that text from the output 
>> and use only the rest. Then he would not have to obey the conditions on 
>> redistribution of the copied text.
> 
> This says to me that you can consider LSR snippets as part of the code used 
> to create music (any music, not just your specific music).  You can then put 
> your specific music in a separate file, with separate copyright.  And the 
> modified LilyPond (including the LSR snippets) is a derivative work of 
> LilyPond, and has GPL rights, and you would be required to share all of that 
> code.  But the created music engraving (pdf, svg, or midi) is not a 
> derivative work of LilyPond, but an output of the program lilypond, and 
> cannot be restricted by the GPL, according to the FSF.

The snippets should be LGPL for being includable under other licenses, I 
believe, because the processed part remains in the output, and thus 
copyrightable. Thus, they play the same role as the Bison skeleton file and GCC 
libraries.