Re: [eigen] Important: Relicensing Eigen to MPL2

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On 16.01.2012 04:02, Benoit Jacob wrote:
*** Main questions to answer ***
1. Would you agree to a MPL2 relicensing of the code you've
contributed to Eigen?

b) yes

2. Would you personally consider such a MPL2 relicensing of Eigen a
good or a bad thing?
     a) Clearly a good thing
     b) Somewhat of a good thing
     c) Neither a good nor a bad thing
     d) Somewhat of a bad thing
     e) Clearly a bad thing
     f) Don't know

I'll go for a mixture of c) and f) ;)

3. Which of the following courses of action would you consider the
best choice for Eigen?
     a) Keep current LGPL3+/GPL2+ license
     b) Relicense to MPL2
     c) Relicense to a liberal license (MIT/BSD).
     d) Relicense to some other license (please elaborate).

I would go for the most liberal license for which there is a consensus amongst developers (I'm not really a license expert, so don't expect any elaborations, which license that might be).

Notice that the present MPL2 relicensing proposal would not exclude,
if accepted, a future relicensing when the time comes. [...]

As long as all authors agree you can re-license as often as you want, can't you? Or are there any licenses that would explicitly prohibit re-licensing?

*** What are the problems we're trying to solve, with the current
Eigen licensing? ***

1. Excessive complexity of the LGPL is scaring away potential users

I agree, it's been some time that I read the complete (L)GPL, and I certainly don't remember (or never cared about) many details ...

2. The LGPL doesn't allow some things that we need to allow
[equal license for source and documentation ...]

Yes, that's certainly a defect for LGPL.

*** OK, so the LGPL isn't great. What are the other licenses we can
choose from? ***

One obvious answer is "BSD/MIT" but it is clear from private
conversations that there is opposition to that from a very significant
part of the project members. So while I can't rule out the possibility
that we'd some day relicense to such liberal licenses, this can't
happen in the near/foreseeable future. We need a better license than
the LGPL, sooner.

Mostly out of curiosity: What are the current concerns against BSD/MIT?

The LGPL is a weak-copyleft license. In order to get relicensing
consensus fast, we need to stay within the bounds of the
weak-consensus realm. The only somewhat widespread weak-copyleft
licenses that I know, are:

I've never ever heard of CeCILL-C before reading this thread (but again, I'm no expert ...)

*** How is the MPL2 better? ***

1. The MPL2 is 2.8x shorter than the LGPL (including GPL, of which it
is an addendum), see above table.

2. The MPL2 is much better written than any other copyleft-ish license
I've seen. See for example these definitions from the MPL2:

     1.6. “Executable Form”

        means any form of the work other than Source Code Form.

     1.13. “Source Code Form”

        means the form of the work preferred for making modifications.

Sorry, but that still confuses me:
Wouldn't that mean a tar.gz version of the source is an "Executable Form"?
I see the point that you want to prohibit declaring obfuscated versions of the source being declared as "Source Code Form". Maybe something like "any form which can't be converted to Source Code Form" would have been more clear? Although, I wouldn't say that an encrypted archive of the source is in any way "executable" ...

*** Should we relicense to MPL2-only or tri-license MPL2/LGPL/GPL? ***

We should do MPL2 only. Mozilla has been tri-licensing MPL/LGPL/GPL
for a while and that is considered a big mistake. It allowed people to
screw us by forking mozilla code and releasing it under GPL only,
preventing us from using it.

Above you mentioned, that Eigen already uses GPL/BSD modules, so I wouldn't see a real problem with that. Well, maybe if someone makes some big internal changes in Eigen that could be a problem.

O.t.o.h, I agree that more licenses rather make things more complicated (for the developers/maintainers). Especially, everyone who want's to contribute to Eigen would have to agree on all three licenses.


Dipl.-Inf. Christoph Hertzberg
Cartesium 0.051
Universität Bremen
Enrique-Schmidt-Straße 5
28359 Bremen

Tel: (+49) 421-218-64252

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