[eigen] Switch to LGPL 3 ?

[Benoît Jacob <jacob@xxxxxxxxxxxxxxx>]

Hi List,

Last time I proposed a switch to LGPL 3, the main objection was compatibility 
with KDE. Now that KDE is switching to LGPL3/GPL3, this objection vanishes.

You probably saw my CC'd mail to the FSF discussion list. It is being held for 
moderation as I'm not a member, I don't know for how long, anyway I don't 
hope much anymore from it.

I have looked at the LGPL text and I think I am confident enough that the 
needed changes have been applied to the LGPL, in order to make it usable for 
us.

Quoting http://www.gnu.org/licenses/lgpl.html :

> “The Library” refers to a covered work governed by this License, other than
> an Application or a Combined Work as defined below. An “Application” is any
> work that makes use of an interface provided by the Library, but which is
> not otherwise based on the Library. Defining a subclass of a class defined
> by the Library is deemed a mode of using an interface provided by the
> Library. A “Combined Work” is a work produced by combining or linking an
> Application with the Library. The particular version of the Library with
> which the Combined Work was made is also called the “Linked Version”.

So far so good: the above definitions handle the non-linking case. Anyway, the 
following section handles explicitly the case of #included code:

> 3. Object Code Incorporating Material from Library Header Files.
> The object code form of an Application may incorporate material from a
> header file that is part of the Library. You may convey such object code
> under terms of your choice, provided that, if the incorporated material is
> not limited to numerical parameters, data structure layouts and accessors,
> or small macros, inline functions and templates (ten or fewer lines in
> length), you do both of the following: a) Give prominent notice with each
> copy of the object code that the Library is used in it and that the Library
> and its use are covered by this License. b) Accompany the object code with
> a copy of the GNU GPL and this license document.

This is a bit annoying in my opinion, but keep in mind that in the case of a 
traditional linked library, there are even more annoying clauses and nobody 
seems to complain. I have a feeling that these clauses are often overlooked 
and nobody cares to enforce them, which is a perverse situation, but I'm not 
out there to solve all the problems of software licensing.

So, OK to relicense?

I'm interested in everybody's answers, especially Michael's as he holds a 
copyright on one existing file.

Cheers,

Benoit

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