[License-discuss] Differences between GPL and LGPL

John Cowan cowan at mercury.ccil.org
Thu Jan 3 14:30:33 UTC 2013

Engel Nyst scripsit:

> If I use an LGPL software in my application, without modifying its
> code in any way, it's probably safe to say I can license my code in
> any way. Including what is declared as GPL-incompatible licenses for
> the rest of the code.

That's true, provided the other licenses are not incompatible with each
other, of course.

However, when you deploy your software, you must provide the LGPLed
source code, *including* any modifications you have made.  Furthermore,
you must make it technically reasonable for a user to replace the LGPLed
code with other code (though the software does not have to still work
after that is done).  The easiest way to do that today is to make sure
it is packaged in a shared library; if you are supplying static object
code, you have to provide it in a form that is easy to re-link with the
replacement code.

For these reasons, you can't incorporate an LGPLed chapter into a
proprietary printed book, since the user can't easily replace the
chapter with another -- unless you supply an editable ebook format,
which is why the (L)GPL isn't encouraged by the FSF for books.

These restrictions are too often ignored in practice.

John Cowan  cowan at ccil.org   http://www.ccil.org/~cowan
O beautiful for patriot's dream that sees beyond the years
Thine alabaster cities gleam undimmed by human tears!
America! America!  God mend thine every flaw,
Confirm thy soul in self-control, thy liberty in law!
        --one of the verses not usually taught in U.S. schools

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