[ From http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/license.html]

Licenses for the Library

There are two licenses affecting GNU libstdc++-v3: one for the code, and one
for the documentation. Here we will describe both of them, and try to answer
some of the widespread questions. If you have more questions, ask the FSF or
the gcc mailing list; the person writing this page is a programmer, not a
lawyer.

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The Code: Runtime GPL

The source code of libstdc++-v3 is distributed under version 2 of the GNU
General Public License, with the so-called "runtime exception," as follows
(or see any header or implementation file):

   As a special exception, you may use this file as part of a free software
   library without restriction.  Specifically, if other files instantiate
   templates or use macros or inline functions from this file, or you compile
   this file and link it with other files to produce an executable, this
   file does not by itself cause the resulting executable to be covered by
   the GNU General Public License.  This exception does not however
   invalidate any other reasons why the executable file might be covered by
   the GNU General Public License.


Hopefully that text is self-explanatory. If it isn't, you need to speak to
your lawyer, or the Free Software Foundation.

Q: So any program which uses libstdc++ falls under the GPL?
A: No. The special exception permits use of the library in proprietary
applications.

Q: How is that different from the GNU {Lesser,Library} GPL?
A: The LGPL requires that users be able to replace the LGPL code with a
modified version; this is trivial if the library in question is a C shared
library. But there's no way to make that work with C++, where much of the
library consists of inline functions and templates, which are expanded
inside the code that uses the library. So to allow people to replace the
library code, someone using the library would have to distribute their own
source, rendering the LGPL equivalent to the GPL.

Q: I see. So, what restrictions are there on programs that use the library?
A: None. We encourage such programs to be released as open source, but we
won't punish you or sue you if you choose otherwise.

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The Docs: FDL

The documentation shipped with the library and made available over the web,
including the pages generated from source comments, are copyrighted by the
Free Software Foundation, and placed under the GNU Free Documentation
License version 1.1. There are no Front-Cover Texts, no Back-Cover Texts,
and no Invariant Sections.

If you plan on making copies of the documentation, please let us know. We
can probably offer suggestions.

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Comments and suggestions about this page are welcome, and may be sent to the
libstdc++ mailing list. Comments or questions about the licenses themselves
are also welcome, and should be directed to the GCC list as descibed above.

