Raul Miller wrote:
The non-GPL copyleft license I've most frequently encountered is the LGPL.
If A is GPLed and B is LGPLed, it's legal to produce C which is derived
from A and B without getting any further permissions. [B isn't the GPL,
but its terms do not impose anything which is more restrictive than the
GPL's terms.]
Thus, I believe that your "I can't produce" assertion can not always be
the case.
That said, people licensing their code under the LGPL often also license
it under the GPL so that people can drop the LGPL license if they wish.
Thus, even if the LGPL were somehow incompatible with the GPL, there
would still be examples of B where you wouldn't need further permissions
to derive a work from A and B.
As I understand the LGPL, section 3 ensures that anyone who receives a
copy of an LGPL work has the option of relicensing it under the GPL.
Therefore, the LGPL is compatible with the GPL because the work is
effectively licensed under the GPL as well.
LGPL section 3:
"
3. You may opt to apply the terms of the ordinary GNU General Public
License instead of this License to a given copy of the Library. To do
this, you must alter all the notices that refer to this License, so that
they refer to the ordinary GNU General Public License, version 2,
instead of to this License. (If a newer version than version 2 of the
ordinary GNU General Public License has appeared, then you can specify
that version instead if you wish.) Do not make any other change in these
notices.
Once this change is made in a given copy, it is irreversible for that
copy, so the ordinary GNU General Public License applies to all
subsequent copies and derivative works made from that copy.
This option is useful when you wish to copy part of the code of the
Library into a program that is not a library. "
--
Lewis Jardine
IANAL IANADD
