On Wednesday 18 February 2009 12:00:11 am Charles Oliver Nutter wrote:
> Conrad Meyer wrote:
> > Keep in mind, GNU readline is GPL. So I think in order to keep JRuby's
> > license as permissive as it is, you'll need to use editline instead (a
> > non-GPL readline replacement).
>
> Well, that's certainly something to consider, but of course we wouldn't
> actually copy, distribute, or modify readline. readline-ffi could either
> be shipped with JRuby (under JRuby's licenses) or shipped as a separate
> gem (requiring users to install it for readline support in jirb). But as
> it stands now, there's very little monitoring or consideration for the
> license of a Ruby gem compared to the implementation or application you
> load it from. So then we mostly have the dynamic linking of readline to
> consider.
>
> Disclaimer: IANAL, and this is fuzzy territory even for people who are.
>
> Most definitions of GPL I've read lately exclude cases of dynamically
> linking in a library. This post describes a number of reasons why this
> is likely a safe assumption:
>
> http://lwn.net/Articles/172248/
>
> The basic premise being that the GPL itself says that it does not cover
> "activities other than copying, distribution and modification", and that
> "the act of running the Program is not restricted". So based on those
> clauses alone, as long as we're not distributing GPL-only code and we
> can run if said code is not present on the target system (both of which
> apply to readline/readline-ffi), we can legally link to that code.
>
> But of course IANAL. I feel more comfortable with the ambiguity at this
> point, and I personally wouldn't worry much if we shipped readline-ffi
> directly in JRuby.

I was under the impression that non-GPL code could not link statically or 
dynamically with GPL libraries, and that this was one of the major differences 
between the GPL and LGPL. This is certainly Stallman's opinion (he cites 
readline as an example of why to license a library GPL instead of LGPL 
specifically so that GPL programs have an "advantage"). But you are right, 
Stallman isn't a judge. And readline is GPLv2+, so the last comment on that 
LWN article about GPLv3 explicitly mentioning linked works doesn't support my 
original claim.

Nokia/Trolltech is another example of a non-judge that believes non-GPL 
programs can't link against GPL libraries (or they wouldn't have needed to 
relicense Qt as LGPL).

I think linking dynamically against readline and claiming to be more 
permissive than GPL is sort of legally weak (but IANAL). Still, maybe it's 
safer for your users to look into using editline instead of readline (this is 
exactly why editline was created anyways).

Regards,
-- 
Conrad Meyer <kon...@tylerc.org>


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