[R-pkg-devel] Changing License

| It has come to my attention that some of the code I am distributing in one
| of my packages was previously licensed under the MIT license.  I have
| previously released my package under the GPL-3 license.  Would it be more
| appropriate for me to change the license to MIT?  I know no one here is
| likely a lawyer but I would like to hear if there is any issue in changing
| a license of a currently released package as it is my understanding that my
| package should have the MIT license instead.

It is my understanding that this is "additive" where licenses are compatible.

Look eg at R itself. It is under GPL-2+ but contains code from other folks
released under compatible licenses -- as document more precisely in this file

  https://github.com/wch/r-source/blob/trunk/doc/COPYRIGHTS

which enumerates which files (or sets of files and directories) have
different copyrights as well as licenses (these terms frequently get mangled,
this file does too).

As another reference point, Debian formalised something similar in the
prescribed format for debian/copyright files (typically installed as
/usr/share/doc/${PACKAGE}/copyright for a given package) where sets of files
are enumerated and both the copyright and license are stated.  See eg

  https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/

for all the gory details.

So in short, I think you can simply include a file stating which of the files
you re-use are copyrighted by which authors and released under which
license. _Your work extending and using those files_ as contained in your
package can happily remain under GPL-3 as does the aggregation, while the
components your refer to remain in eg MIT.

Makes sense?

Dirk
#notALawyerDisclaimerIfYouNeedIt

http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

Hi,

we had a related discussion some time ago in the JSS editorial board. It 
was a long and partly emotional discussion of the pros and cons, but the 
good news was that if a code is MIT, it can be re-licensed as GPL, while 
it would not not be possible in the opposite direction (except by the 
original copyright holders).

MIT is less political and more permissive than GPL, but its disadvantage 
is that someone can take your code, create derived work and then sell 
the derived work as closed source. Even the original developers may be 
excluded from derived work, or have to pay for it.

The JSS board discussion ended with a request in 
https://www.jstatsoft.org/pages/view/authors
that

"Code needs to include the GNU General Public Licence (GPL), versions 
GPL-2 or GPL-3, or a GPL-compatible license for publication in JSS."


where MIT or BSD can be considered as GPL compatible, while packages 
with some other licenses my need explicit double-licensing by the 
copyright holder, see also:

https://en.wikipedia.org/wiki/License_compatibility

"Many of the most common free-software licenses, especially the 
permissive licenses, such as the original MIT/X license, BSD licenses 
(in the three-clause and two-clause forms, though not the original 
four-clause form), MPL 2.0, and LGPL, are GPL-compatible. That is, their 
code can be combined with a program under the GPL without conflict, and 
the new combination would have the GPL applied to the whole (but the 
other license would not so apply)."


I would therefore recommend GPL, and you don't make something wrong if 
you re-license derived work using MIT-licensed code under the GPL.

Thomas

PS: this is my personal conclusion, I am not a lawyer.

Dr. Thomas Petzoldt
http://tu-dresden.de/Members/thomas.petzoldt