John Cowan jcowan at reutershealth.com
Thu May 19 17:17:49 UTC 2005

Zeno Davatz scripsit:

> Can anybody point me to a nice summary of the main differences between
> the LGPL and the GPLv2?

In brief, it is as follows:

An LGPLed library can be used and distributed as part of an application
for which full source is not provided.  However, you must distribute the
source for the library itself, and you must follow all the GPL rules if
you modify the library.  Furthermore, you must make it possible for the
user to relink the application with a new version of the LGPLed library,
though you are not required to make the application actually *work*
with the new version.

This last point can be achieved by making the LGPLed library a .so or
.dll file, or by distributing your code as a library or as object files.
In Java it's automatic, because dynamic linking is the only kind of

There is an ongoing controversy whether subclassing a class in an LGPLed
library requires your class to be licensed under the LGPL.  IMHO it does
not, but the FSF has not specifically ruled on the question (nor are
their rulings necessarily authoritative in court).  In a library designed
for subclassing, my view is that subclassing is use, not modification;
others may disagree.

I am not a lawyer; this is not legal advice.

Business before pleasure, if not too bloomering long before.
        --Nicholas van Rijn
                John Cowan <jcowan at reutershealth.com>
                        http://www.ccil.org/~cowan  http://www.reutershealth.com

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