RE: [Gcl-devel] GCL GPL/LGPL license

[Mike Thomas]

Hi Eric.

Welcome to GNU Common Lisp (GCL).

I won't go into the details of the GNU licences (General Public Licence
(GPL) and (Lesser General Public Licence) in this email but rather, will
give a very brief summary and refer you to the GNU web site for context and
further reading:

  http://www.gnu.org/licenses/licenses.html

In short you may, if you wish, build a proprietary application with GCL
provided that you do not include components such as BFD and UNEXEC which are
covered by the GPL.

Quoting from:

  http://www.gnu.org/licenses/why-not-lgpl.html

"The GNU Project has two principal licenses to use for libraries. One is the
GNU Library GPL; the other is the ordinary GNU GPL. The choice of license
makes a big difference: using the Library GPL permits use of the library in
proprietary programs; using the ordinary GPL for a library makes it
available only for free programs."

In the discussion that follows, you need to remember that GPL is more
restrictive than LGPL and therefore takes precedence in a software project
which contains some parts GPL, and others LGPL.


|  I am playing with gcl a bit again and I am a little
| confused about the license. According to the splash it
| says that the gcl binary is under gpl but source is
| under lgpl. How does the apply to the creation and
| distrobution of applications?

The GCL licence reflects the fact that our source tree includes various
components with different licences.

If you build a binary with just LGPL components then your binary in turn
remains LGPL.

If, instead, you include some components which are LGPL and others GPL, then
the overall licence is GPL because GPL is the more restrictive of the two
licences and therefore gains precedence.


For example, on my Windows system I get the following 2 lines:

  Source License: LGPL(gcl,gmp), GPL(unexec,bfd)
  Binary License:  GPL due to GPL'ed components: (UNEXEC)

This means that my binary and anything I link with that binary is GPL,
because it includes binary code built from the unexec source code which is
itself covered by the GPL.

It also tells you which parts of our source tree are GPL and which LGPL.


|  I realize this is somewhat open ended, but I am just
| not sure what effect this license has on my (possible
| future) applications.

It is entirely possible to build an application covered only by the LGPL
from the GCL source tree.  That application is therefore able to benefit
from the commonly used commercial intellectual property protection strategy
of source code secrecy; you just need to link it without BFD, UNEXEC or any
other GPL item that may, from time to time, find its way into our source
tree.

You also have the opportunity to protect your software with the GPL, thereby
taking the first step to ensuring that any contribution you make to the
world community remains free for all to use and develop, in the public
arena.

Cheers

MIke Thomas.