Re: [Bug-readline] How to determine the GPL version at compile and run time ?

[Chet Ramey]

On 6/14/14, 4:19 AM, Thomas Schmitt wrote:
> Hi,
> 
> GPLv2+ licensed libisoburn includes <readline/readline.h> which on
> my system says
> "GNU General Public License [...] either version 2, or (at your option)
>  any later version."
> 
> Nevertheless, there is a Debian bug which indicates that meanwhile
> the license of their libreadline is GPLv3+.
>   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=749801

Readline's license changed from GPLV2+ to GPLV3+ between readline
versions 5 and 6, with version 6.0 released in February 2009.  The current
version is 6.3.  It's entirely possible that libisoburn includes a
copy of readline 5.2.

> 
> libisoburn states its license GPLv2+ in human readable output.
> But i understand this is not true anymore if the GPLv3+ version
> of libreadline is included and/or linked.
> For clarity, i want to adapt that human readable text.
> 
> So how do i find out at compile time and especially at run time
> what GPL version is granted by libreadline ?

There is no way to do it other than looking at the value of the
RL_VERSION_NAJOR define in readline.h.  If it's at least 6, that
version of readline is licensed under GPLV3+.

> 
> Would it be legal to link a program, that was compiled with
> the GPLv3+ header, with a libreadline.so that is under GPLv2+ ?
> Does libreadline prevent such a license mix ?
> Does libisoburn have to prevent it ?
> How much obligation for own effort is legally imposed on users of
> libreadline ?

These are mostly questions for address@hidden, but readline does nothing
to prevent such theoretical version mismatches.  It's unlikely, however,
that a program compiled using readline version 5 headers would work
without problems when linked with readline version 6.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/