GPL compatibility (was: Re: French GPL-compatible License)

Alex Hudson home at
Mon Jul 12 22:38:51 UTC 2004

On Tue, 2004-07-13 at 00:04 +0200, Thomas Linden wrote:
> On Mon, Jul 12, 2004 at 10:52:49PM +0100, Alex Hudson wrote:
> > You can never relicence other people's code. The GPL doesn't allow you
> > to do that either - so, I don't think you're right to call the GPL
> > "infecting".
> The GPL forces me to relicense code - my code.

No, it doesn't. You can take someone else's BSD code and combine it with
someone else's GPL code and release the lot. You don't need to relicense
any code, which is why they are "compatible". You just have to respect
*both* licences. It doesn't require you to relicense code - either
yours, or anyone else's (which you cannot relicense, even if you wanted

> the GPL *tells* me that the resulting code must also be released
> under the GPL.

It says that you have to respect the GPL licence (i.e., that you release
it complying with the terms of the GPL). In practice, this means that
the licence terms for the whole cannot be more restrictive than the GPL,
but if you disagree with that then it's not the GPL you have a problem
with but Copyleft in general. 

> The BSD license on the other hand does not tell me how I do have to
> license my code. I can use bsd-licensed code however I like, I don't
> have to release the resulting source under some bsd license; this
> allows me to create a new GPL project which includes e.g. FreeBSD
> code. 

That's not right. If you take someone else's BSD code, you cannot
relicense it. You have no rights to do that - you must respect the BSD
licence. Hence the "problems" with the original BSD licence that had an
advertising clause. If you could relicense BSD code, that problem would
have vanished as people just relicensed things to a different licence.

> So, there is definitively a difference which makes them
> incompatible. This is the cause why most (I'm not sure if this is the
> case for all) BSD base systems do not include GPL code.

BSD systems tend not to include GPL code because they are a cohesive
whole (an entire operating system), and they wish to have uniform
licensing. The BSD licence is the one they have chosen, that's why they
do not accept BSD code. All big projects will only accept code licenced
under certain terms; Linux only accepts GPL code, for example. BSD just
happens to include many separate utilities.

> I don't want to flame against the GPL (I use it in my own projects),
> but it is not the holy grail, and I don't see, why people "should"
> use a gpl-compatible license.

GPL compatibility is important for a number of reasons. Firstly, there
is a huge amount of free software licenced under the terms of the GPL -
so, for purely practical reasons, something which is licenced compatibly
with the GPL is likely to be usable in combination with as much other
software as possible. This is ignoring any potential ideological reason
you might have for choosing one over another.

Also, if it's GPL compatible then it's using a well-known licence that
people understand - if it was under some new licence that was not GPL
compatible, people would have to analyse the licence to make sure that
it really was a free software licence. 



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