[Haskell-cafe] short licensing question

Svein Ove Aas svein.ove at aas.no
Mon Jan 11 08:15:24 EST 2010

On Mon, Jan 11, 2010 at 2:08 PM, Don Stewart <dons at galois.com> wrote:
> sebf:
>> Hello Café,
>> when writing a Haskell library that uses two other Haskell libraries --
>> one licensed under BSD3 and one under LGPL -- what are allowed
>> possibilities for licensing the written package? PublicDomain? BSD3?
>> LGPL?
> Libraries don't link in other things as such -- the .cabal file is the only
> thing that ties them together -- so you can use whatever license you
> like.
> Any resulting binaries might contain a mixture of such libraries, and
> the most restrictive license will usually be the license of the result.
So, let's look at binaries then.

In this case, LGPL is a problem. It requires you to offer a way to
re-link such binaries against new versions/implementations of the
library, which in practice requires it to be either open source or
dynamically linked.

Dynamic linking doesn't exist in GHC 6.10 and below. LGPL is thus
restricted to open-source applications there.

In 6.12.. well, dynamic linking exists, but in practice trying to
replace a library implementation won't work. In fact, there's code in
specifically to prevent it from working (well, crashing, really). So
LGPL isn't very useful on that either.

In practice, then, LGPL'd haskell libraries are probably useless for
the stated purpose of supporting closed-source applications. You'd
have to modify the license, or rather find something that fits better.
I'm sure that exists, and chances are the author will be understanding
if you ask.

Svein Ove Aas

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