In a sense this question is an extension to How should I mark a source file with GPLv2 as a derivative work?.
I would like to publish a project where it frequently occurs that files are drived works of multiple GPLv2-licensed original files.
- each original file carries a GPL preamble with a copyright notice
- some files carry additional/secondary copyright notices below that preamble, probably predating the original project's move to GPL
- the GPL preamble of each file states that the header and copyright notices must not be changed
- the copyright notices in the GPL preambles slightly vary in the year and occasionally in the holder
- in one file the copyright notice is even missing
So, I believe that the right way would be to proceed like answered in How should I mark a source file with GPLv2 as a derivative work?, but clearly state from which original files the file is derived and list each file's preamble, including the additional/secondary if present. Each such preamble entry would be "decorated" with the original filename to track where it comes from.
However, some files derive from 20 or more original files. So all the individual preambles would bulk significantly.
- Is it acceptable to "compress" the list by stating the GPL preamble only once, with the combined years and copyright holders form all the files it is derived from?
- Is it acceptable to just list the various secondary copyright notices below that GPL preamble without indicating which comes from which original file?
- Is it acceptable to unify duplicates from that list (merging the specified years), as this means that it wouldn't be tracked any more which notice stems from which file?
- Is there some other (entirely different?) policy to handle such cases?
All questions assuming that the policy to combine the file preambles is explained at the top.
I believe that whatever the answer is, it is probably applicable to GPLv3 as well. However it would be good if an answer would drop a note on whether it also applies to GPLv3 if known.