[cairo] Re: License for cairo changed to LGPL

[Keith Packard]

Around 18 o'clock on Aug 4, "M. Evans" wrote:

> To my mind, the wx approach is a very good middle ground.  It lets
> businesses sell binaries with or without library changes, and without
> worrying about the definition of "linkage."

One reason for the switch to LGPL is precisely to avoid 'hidden' changes 
like these.  We really do want to see any changes people need to make in 
cairo for whatever weird environment they're using.  To my mind, the wx 
license is no more effective at this than the MIT or BSD licenses.

Basically, if you use cairo, we want to see what you've done with it, but 
not any code outside of cairo.  The LGPL provides a reasonably coherant 
description of what changes are "within the library" by requiring that the 
user be able to (in theory) replace the version of the library used within 
the resulting product.  The goal is to make it possible for people to use 
cairo without disclosing their own code, while still sharing any changes 
they've made to cairo itself.

Yes, the LGPL is far from perfect, but combining that with a reasonable
statement of our goals for the license yields something a lot closer to
what we want to achieve than any other OSI approved license.  I submit that
having us create a new license is a really bad idea.  

Perhaps the OSI will be approached with a better license than the LGPL for
this purpose; if so, we can always revisit the whole issue at that point
(not that I really look forward to another relicensing adventure, but it's
always possible).  

We aren't requiring copyright assignment for including code in cairo, so we
will always need the consent of all contributors before changing the
license; one goal of this is to make changing the license "hard" --
something we learned when The Open Group relicensed the X window system
years ago.  We do, however, currently insist that all of the code remain
under a single license, and I can promise to hold to that policy in the 
future.

I don't think too many places have a problem with understanding the basic 
requirements of the LGPL in various contexts; that leaves them with a 
pretty simple choice when deciding whether to use cairo or not.

The tradeoff is fairly simple -- the LGPL means we get to share the changes
needed to run cairo in weird environments and we get to make sure the
public version remains the best available at the expense of possibly losing
a few embedded applications of the library.

Given my experience with the MIT license used within the X window system, I
think the LGPL will serve cairo better over the long term, even if we 
lose a few "customers" at times.

-keith


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