On Sat, 12 May 2007 12:41:58 +0100
"Marcus D. Hanwell" <[EMAIL PROTECTED]> wrote:

> There is a template library called Eigen I would like to add to the
> tree. It is a dependency of an application I would like to add
> shortly. It will also end up being a dependency of KDE 4 (for
> kalzium). My question relates to the licence the code is released
> under.
> 
> It is licenced under the GNU GPL, version 2 or later with the
> following exception,

This is a common situation with GPL compilers - some are licensed
so that they can be used to build non-GPL software, some can only be
used to build GPL software.

The situation with Eigen is similar to the "libgcc exception" for GCC.
We don't mention that in the LICENSE for gcc.  This is the exception
that allows you to build non-GPL software with gcc (note for the
interested - if you build profiled executables with gcc, the GPL applies
to the built executable since the profile support code linked into the
executable is licensed purely under the GPL - not a real problem as
no-one distributes profiled executables!).

However there's also a similar exception for gnat-gcc; that has a
separate license file GMGPL which explains the situation there.
However this is talking about extra libgcc stuff that is
Ada-specific - the standard libgcc exception is not mentioned.
For information, gnat-gpl (the AdaCore-sponsored version) doesn't have
the exception, so is straight GPL - this also means you can't use
gnat-gpl to build and distribute BSD-licensed software, for example.

So currently we're inconsistent.  We must be accurate in our license
declarations, I think, so my view is if Eigen has a license that is GPL
with some exception, that should be made clear.

All these exceptions are doing the same thing - relaxing the GPL as it
applies to the compiler (or template library in this case), so that it
does not apply to works created using it.  I like the
"GPL-2-with-linking-exception" license name that the gnu-classpath
package uses; perhaps we could include (concatenate) all the exception
clauses that lead to the same thing into that license file and have the
relevant packages use that license name.

-- 
Kevin F. Quinn

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