Guideline to linking in a multilicense situation

[Tom "spot" Callaway]

On Fri, 2008-05-30 at 17:20 +0200, Yaakov Nemoy wrote:
> Hi List,
> 
> My mentor would like to use a library for part of his GSoC work that
> is licensed partially under the BSD license and partially under the
> Apache License.  The library is PlotKit and can be found here:
> 
> http://www.liquidx.net/plotkit/
> 
> As far as bundeling the library, we can always encourage him to create
> a separate package for Fedora, so that we can ship Smolt as a GPL2
> only package with a dependency.  In terms of GSoC related things, it's
> one more way to encourage him to join the community, of course.  My
> only question is though, are we allowed to link to this library?  I'm
> afraid I don't quite understand the nuances of a mixed license
> environment.  Or would we need to fork the library to match licenses?

Off the cuff (I've not looked at plotkit, or what you want to link it
to)...

If plotkit is under both the BSD and the ASL 2.0 (yes, it does matter
what version of the Apache license it uses), any linking would need to
meet the terms of both licenses. ASL 2.0 is GPLv2 incompatible, but
GPLv3 compatible. If Smolt would depend on PlotKit, this would be
problematic (unless Smolt is GPLv2+, in which case, the complete work
would likely be interpreted as GPLv3).

Alternately, Smolt could add an exception permitting linking to code
under the Apache 2.0 license, something like:

  In addition, as a special exception, [the copyright holder] gives 
  permission to link the code of its release of Smolt with the 
  "PlotKit"  library (or with modified versions of it that use the same 
  license as the "PlotKit" library), and distribute the linked 
  executables. You must obey the GNU General Public License in all 
  respects for all of the code used other than "PlotKit". If you modify 
  this file, you may extend this exception to your version of the file, 
  but you are not obligated to do so. If you do not wish to do so, 
  delete this exception statement from your version.

You'd need to get permission of the copyright holder to do this, which I
suspect is Red Hat, Inc. If you want to go down this path, email Richard
Fontana <rfontana at redhat.com> directly and CC me.

~spot