LGPL 2.1 + GPL 3 = problems?

John Cowan cowan at ccil.org
Sun Jul 15 15:01:27 UTC 2007

Jesse Hannah scripsit:

> Would using (linking, including/redistributing unmodified) a library
> that's licensed under the LGPL version 2.1 with a program that's
> licensed under the GPL version 3 cause any weird problems?

No, it would not.

> My initial guess is that just linking the libraries, or redistributing
> the source code unmodified---either entirely separate from, or something
> like in its own folder in the same package with the GPL'd code---
> would be fine,

Quite right -- not because of the special features of the LGPL that
allow conversion to the GPL, but because the whole point of the LGPL
is that an LGPLed library can be combined into a larger work that
uses the library, and this larger work may have any desired license
consistent with the licenses of its non-LGPL components,
even a proprietary one.

For example, one may combine an LGPLed library with a BSD-licensed
main program and license the whole work under the BSD, or the GPL,
or a proprietary license.

> but any copy-and-paste inclusion, modification and attribution might
> raise some eyebrows and/or compatibility issues (like I said, I'll be
> reading the fine print one more time to see if I can spot anything).

Indeed.  You cannot physically incorporate nontrivial amounts of
code (whatever is beyond fair use) from an LGPLed library into a
work with a license other than LGPL or GPL, and GPL only if you
convert that copy of the code irrevocably to the GPL.

John Cowan                              <cowan at ccil.org>
                .e'osai ko sarji la lojban.
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