Re-licensing email

Matt Mackall mpm at selenic.com
Wed Oct 14 12:19:25 CDT 2009


On Wed, 2009-10-14 at 08:33 +0100, Frank Kingswood wrote:
> Hallo!
> 
> I got a surprising email this morning regarding relicensing Mercurial under 
> GPLv2+. There was (apart from the Mercurial-must-follow-Eclipse-license 
> thread) not any recent discussion on the mailing list about this.

This follows from the cvs2svn license discussion.

I took the issue up with our lawyers at the Software Freedom Law Center,
and had a fairly lengthy back and forth about all the possible loopholes
and counterarguments.

Turns out this is mostly an issue for distributors, who might make a
combined work by shipping Mercurial and SVN bindings together (the
TortoiseHG folks would also like to do this). Also, the folks working on
two-way Mercurial<->Subversion clients are impacted too. Being in a
situation where we're not clearly abiding by other people's licenses
while asking them to abide by ours makes me unhappy, so I decided I
should probably do something to make the situation less ambiguous.

As a result of that conversation, I came away with the following
options:

a) remove SVN support
b) relicense with a special SVN exception
c) rewrite SVN bindings to communicate via command line
d) rewrite SVN bindings to read/write SVN repos directly
e) relicense with GPLv2+

We didn't go with (b) because I already get a couple requests a month to
add exceptions and exceptions actually make more trouble for people. The
folks on crew thought (c) and (d) were prohibitively difficult and I
certainly didn't want to do the work. And (a) would have obviously made
many current and future users unhappy. 

As it happens, most of crew actually preferred GPLv2+ to start with, and
I was easily the most significant objector to v3. So I spent an
afternoon rereading the v3 license and eventually came to the conclusion
that none of my objections to it were significant enough in the context
of Mercurial to continue blocking it.

Pragmatically, this will only make lives for developers of Mercurial and
related projects easier, while still meeting my personal requirement of
maintaining a strong copyleft. So, I decided to hold my nose and go for
(e).

I didn't post it here first because I actually want to get useful work
done sometime this month.

By the way, we will not be accepting any GPLv3-only contributions any
time in the foreseeable future, so the license will remain GPLv2+.

-- 
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