GPL with the Classpath exception - clarification needed
andrew.wilson at intel.com
Fri Mar 27 00:24:27 UTC 2009
John Cowan [mailto:cowan at ccil.org] wrote:
> The relevant distinction for LGPL purposes is not whether something is
> a derivative work or not: every program that incorporates the library
> into itself is a derivative work. The question is whether the derivative
> work is a "work based on the Library" (LGPL 2.1) / "Modified Version of
> the Library" (LGPL 3.0) or not.
With you so far. Linking to an LGPL library creates a derivative work which
is governed by LGPL.
> Now subclassing a class plainly does not *modify* the class. So programs
> that contain subclasses of an LGPLed class, or instantiations of an
> LGPLed interface, or what have you, are "works that use the Library"
> (LGPL 2.1) / "Applications" (LGPL 3.0) and may be under any license
> provided it is possible to replace the library.
Not quite with you here. Agreed subclassing does not *modify* the base class.
However, are there possible circumstances where a subclass is a derivative
in the copyright sense? If the answer is yes, the rest of your analysis is moot.
Such a subclass, or instantiation, is not a "work that uses the Library."
It is a "work based on the Library," and it is LGPL.
The only exception for a derivative under copyright is the familiar #include rule.
As LGPLv2.1 helpfully notes, "the object code for the work may be a derivative
work of the Library even though the source code is not.... The threshold for this
to be true is not precisely defined by law."
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