On Wed, 13 Nov 1996 00:43:28 +0000 
 "Mark Brinicombe" <amb@physig4.ph.kcl.ac.uk> wrote:

[ I know this isn't Mark's, but I just noticed this comment for the first
  time, and wanted to clarify some things... ]

 > >Yes.  The GPL forbids any redistribution that is under a "less free" (in
 > >the FSF sense) licence.  The BSD licence _is_ less free, and so you cannot
 > >use GPL'd code.  Conversely, the Linux community can't realistically use
 > >any large amounts of BSD code, because to be distributed with the kernel
 > >it would have to adhere to both the BSD and the GP licences, and that's
 > >difficult to achieve in practice.

The main characteristic of the GPL is that the person or group distributing
a GPL'd program or a "derivitive work" of a GPL'd program is required to
make source code for the program or derivitive work available for some
period of time.  You may not charge anything for the code but the cost of
distributing that source code.

In contrast, the "Berkeley-style" (referred to as BSD for the rest of this
post) license states that the software may be distributed in source
or binary-only form, providing proper acknowledgement is given to
the owner of the code (typically, the author).

If you compare the wording of the two licenses, the BSD license
actually gives you much more freedom to do what you wish with
the source code, including use of the source code in a proprietary
product.  The GPL only guarantees that others will be able to
get the source code in the future.

The reason that NetBSD can't use GPL'd code in the kernel is that
the kernel could then be considered a "derivitive work", and thus
any kernel binaries shipped would potentially require the distributor
of that binary to make sources for the entire kernel available under
the terms of the GPL.  The NetBSD Project would like people to do
whatever they wish with NetBSD code, so we choose not to burden users
of the code with the significantly more restrictive GPL.

Linux can incorporate as much BSD code as it wants... the only thing
Linux would have to do is document the copyright notice and give
"due credit" to the owner of the code. It's my opinion that the
reason that Linux _doesn't_ include BSD code, is because they want
to distribute as much as possible under the more restrictive GPL.
Since they can't just change the license on the BSD code, they
have to rewrite the code.

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                               Home: 408.866.1912
NAS: M/S 258-6                                          Work: 415.604.0935
Moffett Field, CA 94035                                Pager: 415.428.6939