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forking a CRAN project

2 messages · Michael Friendly, Peter Dalgaard

Original
Michael Friendly
# 
There is a CRAN package licensed just as "GPL", say, XX, I want to use 
in a book.
But I've needed to modify the package to make it do what I need for 
expository purposes.
The package author(s) are amenable to my modifications, but probably 
unlikely to
incorporate them into the CRAN version any time soon.

Am I allowed, under GPL, to create a new version of the package, say 
XX2, in a
public repository such as R-Forge or github?  I would, of course, 
maintain their
authorship, though perhaps take over the maintainer role.  For my 
purposes in
the book, I don't necessarily need to release my version to CRAN; just a 
public repo
a reader could download from.

-Michael
Peter Dalgaard
# 
As usual: For legal advice, get a lawyer... However, yes, the GPL quite expressedly allows licencees to distribute modified versions, provided that the modified source code is made available and is redistributable under the GPL. 

It's common courtesy and possibly also required by law (the GPL itself doesn't say anything about it) to ensure that the original statements of authorship and copyright are retained. 

One thing to be slightly cautious about is to avoid inadvertent copyright transfer to your publisher of things that are also in the package. The back pages of ISwR (the book) has copies of the help pages for ISwR (the package), but "Reproduced with permission" so that Springer doesn't have the copyright for that part of the book. Not that they are likely to care, but better safe than sorry.

-Peter D
On 04 Mar 2014, at 16:50 , Michael Friendly <friendly at yorku.ca> wrote: