Dispelling BSD License Misconceptions (fwd)

Matthew Flaschen matthew.flaschen at gatech.edu
Wed Jan 17 03:08:43 UTC 2007

Chuck Swiger wrote:
> If they produce a modified version or they combine BSD-licensed code
> with additional software they've written, the portions they wrote or
> changed can be licensed under whatever terms that author wishes
> (assuming for the sake of discussion that the changes are not so trivial
> that they would not merit copyright protection), but the original
> unmodified sources are still under the terms of the BSD license.

Moreover, the portions of their code that were licensed under BSD are
still under BSD (though this usually doesn't mean much).

> There are some people who feel that software licenses somehow
> automatically apply their terms to any and all other software used in
> conjunction with the original software in question (ie, as part of a
> compilation, or via dynamic linking, or via pipelines, RPC, or other
> form of network communication).  

There are many quite distinct conjunctive relationships, which you've
lumped together.  Some forms of conjunction (such as static linking)
clearly create a derivative work, because the original code is present
in the executable.  In most other cases, it is controversial.

> A canonical example is when people
> claim that you can't dynamically link libreadline.so with software under
> another license unless the other software is also under the GPL.
> [ My canonical response to such claims is to have them re-read the
> section of the GPL between clause 2c & 3. ]

You make this sound like the end of discussion.  In fact, this is
probably one of the most complex parts of the GPL.  I urge you to reread
the sentence stating:

"But when you distribute the same sections as part of a whole which is a
work based on the Program, the distribution of the whole must be on the
terms of this License, whose permissions for other licensees extend to
the entire whole, and thus to each and every part regardless of who
wrote it."

The FSF offers guidelines
(http://www.gnu.org/licenses/gpl-faq.html#MereAggregation) about this.
It ultimately comes down to is simply whether the new program is a
derivative work of the GPL-licensed code.  As the FSF says, "This is a
legal question, which ultimately judges will decide."

As far as Readline specifically, A USAGE file says:

"I think Allbery's suggestion is a good one.  So please add this text
in a suitable place.  Please don't put it in the GPL itself; that
should be the same as the GPL everywhere else.  Putting it in the
README and/or the documentation would be a good idea.

Our position on the use of Readline through a shared-library linking
mechanism is that there is no legal difference between shared-library
linking and static linking--either kind of linking combines various
modules into a single larger work.  The conditions for using Readline
in a larger work are stated in section 3 of the GNU GPL."

Obviously, this is interpretation.  Similarly, the FSF uses Readline as
an example of a library they leverage to convince people to release
their programs under the GPL

You're welcome to have a different opinion, but don't try to make it
seem indisputable or uncontroversial by spouting off sections of the GPL

Matthew Flaschen

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