[Haskell-cafe] Re: Re: ANN: hakyll-0.1

Ben Franksen ben.franksen at online.de
Tue Dec 8 17:56:20 EST 2009

Ganesh Sittampalam wrote:
> On Tue, 8 Dec 2009, Tom Tobin wrote:
>> On Tue, Dec 8, 2009 at 3:30 PM, Ben Franksen <ben.franksen at online.de>
>> wrote:
>>> Ketil Malde wrote:
>>>> Your contributions could still be licensed under a different license
>>>> (e.g. BSD), as long as the licensing doesn't prevent somebody else to
>>>> pick it up and relicense it under GPL.
>>>> At least, that's how I understand things.
>>> Right. So hakyll is absolutely fine with a BSD3 license, AFAICS.
>> Seriously, no, this is *totally* wrong reading of the GPL, probably
>> fostered by a misunderstanding of the term "GPL-compatible license".
>> GPL-compatible means the compatibly-licensed work can be incorporated
>> into the GPL'd work (the whole of which is GPL'd), *not the other way
>> around*.  

No. See http://www.fsf.org/licensing/licenses/gpl-faq.html#WhatIsCompatible


"What does it mean to say that two licenses are compatible?

In order to combine two programs (or substantial parts of them) into a
larger work, you need to have permission to use both programs in this way.
If the two programs' licenses permit this, they are compatible. If there is
no way to satisfy both licenses at once, they are incompatible.[...]"

and http://www.fsf.org/licensing/licenses/gpl-faq.html#WhatDoesCompatMean

"What does it mean to say a license is compatible with the GPL?

It means that the other license and the GNU GPL are compatible; you can
combine code released under the other license with code released under the
GNU GPL in one larger program."

>> If you are forming a derivative work based on the GPL'd
>> work, and thus you have to release that derivative work under the GPL.

Maybe, but I doubt very much that publishing a library that merely calls
functions from some other (GPL'ed) library makes your library a "derivative
work" of the former. It is something different if you /combine/ those two
libraries into e.g. an application.

> The combination of haykll and pandoc clearly must be GPL. I don't think it
> automatically follows from that that hakyll taken alone must be GPL.

Right that was the point I wanted to make. It is the responsibility of the
programmer who uses hakyll (and thus, presumably, pandoc) in order to
produce a complete program to make sure that his work complies with /both/
licenses. This is possible if the two licences are compatible, see quotes

> One
> might argue that the hakyll itself must be a derivative work as it builds
> on pandoc, 

If this were so, then /all/ of Linux (including all the thousands of
programs found on linux distributions) would have to be licensed under GPL,
which is clearly not the case.

It would also mean that MS could require fees from people who program
against the windows API.


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