[Haskell-cafe] GPL answers from the SFLC (WAS: Re: ANN: hakyll-0.1)

Tom Tobin korpios at korpios.com
Thu Mar 4 12:34:24 EST 2010

After politely pestering them again, I finally heard back from the
Software Freedom Law Center regarding our GPL questions (quoted

I exchanged several emails to clarify the particular issues; in short,
the answers are "No", "No", "N/A", and "N/A".  The SFLC holds that a
library that depends on a GPL'd library must in turn be GPL'd, even if
the library is only distributed as source and not in binary form.
They offered to draft some sort of explicit response if we'd find it

Maybe it would be useful if Cabal had some sort of licensing check
command that could be run on a .cabal file, and warn an author if any
libraries it depends on (directly or indirectly) are GPL'd but the
.cabal itself does not have the license set to GPL.

On Fri, Dec 11, 2009 at 10:21 PM, Tom Tobin <korpios at korpios.com> wrote:
> I'd like to get these questions out to the SFLC so we can satisfy our
> curiosity; at the moment, here's what I'd be asking:
> Background: X is a library distributed under the terms of the GPL. Y
> is another library which calls external functions in the API of X, and
> requires X to compile.  X and Y have different authors.
> 1) Can the author of Y legally distribute the *source* of Y under a
> non-GPL license, such as the 3-clause BSD license or the MIT license?
> 2) If the answer to 1 is "no", is there *any* circumstance under which
> the author of Y can distribute the source of Y under a non-GPL
> license?
> 3) If the answer to 1 is "yes", what specifically would trigger the
> redistribution of a work in this scenario under the GPL?  Is it the
> distribution of X+Y *together* (whether in source or binary form)?
> 4) If the answer to 1 is "yes", does this mean that a "BSD-licensed"
> library does not necessarily mean that closed-source software can be
> distributed which is based upon such a library (if it so happens that
> the library in turn depends on a copylefted library)?
> By the way, apologies to the author of Hakyll — I'm sure this isn't
> what you had in mind when you announced your library!  I'm just hoping
> that we can figure out what our obligations are based upon the GPL,
> since I'm not so sure myself anymore.

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