Writing an exception to LGPL for a C++ template library

[Federico Montesino Pouzols]

On Wed, October 25, 2006 3:30 pm, Benoit Jacob wrote:
> Thanks for your answers. The reasons why we were considering using the
> LGPL, not the GPL, are that:
> - we need to make sure LGPL-licensed software (apps,libs,everything) can
> use our library without any worry.
> - we don't care too much if proprietary software uses our lib (though we
> wouldn't rejoice about that either).

Both issues can be sorted out with a GPL + exception license. In general,
using LGPL for C++ libraries is a bad idea -I would say. Besides the
"lesser" aspect of the LGPL, it is obsolete in its language (when you
have templates and methods implemented in headers, the division between
the library and the application using it is not a matter of just linking
anymore). In the obsolete language of the LGPL, when you use a template,
you would be basically copying code.

Some FAQs about the libstdc++ "runtime exception" are answered here:
http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/license.html.

To the best of my knowledge, GPL + linking exception is the best way
of extending the LGPL conditions for C++ libraries. Using an exception
similar to that of libstdc++ you will of course allow using your
library in proprietary applications. If you prefer to avoid that
abuse, you could reformulate the exception so that it only allows the
library to be used in GPL and LGPL (or a list of free licenses
acceptable from your point of view) apps and libs.

It seems the eCos license 2.0
(http://www.gnu.org/licenses/ecos-license.html) is also a case of
GPL + exception. This license however adds the restriction that source
code of the app. using the library must be available as specified in
section (3) of the GPL.