M.-A. Lemburg mal at
Mon Aug 9 13:41:39 EDT 1999

Robin Becker wrote:
> In article <37AE9B42.4DF40758 at>, M.-A. Lemburg
> <mal at> writes
> ...
> >If you link against a GPLed product (even if it's done dynamically!),
> >the whole construction (your product + the GPLed one) automatically
> >fall under the GPL. This means that you can still sell and distribute
> >your product, but only if you include the full source code of
> >the GPLed product
> >*plus* your product.
> >
> Oh dear; I wrote this extension called dll for Tcl that allows tcl code
> to link to arbitrary dll's. The source code for the extension is
> available. Must I distribute source for all known GPL'd products which
> can be linked to tcl using this extension. As it happens this thing is
> mostly used by win32ers, but it has run under Linux.

If TCL were under GPL then you'd have to ship both TCL and
your extension under GPL. But you're lucky: TCL is shipped under
a more liberal license, so you can distribute your code in any
form you like with or without TCL, as binary or source.

Note that I just posted this because more and more GPLed extensions
for Python are popping up -- if you want to include these in a
product, you'll have to take some care to follow the extension's
license. Otherwise, including the extension's code would be
simply illegal. In most cases, the author will probably also
distribute his/her code under a different (payed) license. In some
cases (like the GNU readline module, for which Python includes
an extension), the authors will probably not... e.g. shipping
Python with linked in readline support (as DLL or statically)
causes that Python interpreter to fall under GPL and with it,
all extensions linked to it. The Python code run by the interpreter
is not forced under GPL (otherwise all gcc compiled software
would turn GPLed...).

> >The LGPL is a little different: it allows you to link against the
> >LGPLed product without the need to ship your source code. You still
> >have to include the source code of the LGPLed product you're linking
> >against though (including any changes that you have made to it).
> >
> >If you are using Python extensions written by different authors,
> >be sure to check their license statement. In case you have any
> >doubts get in touch with them before using their code. Most
> >extensions are under very similar licenses as Python itself,
> >but some a GPLed and other LGPLed. Also, some are not valid for
> >commercial use meaning that you'll have to negotiate a special
> >license with the author to be able to use in your code. This
> >usually involves paying a license fee.
> >
> >Hope this clarifies things a little. More infos on GPL and LGPL
> >should be available on If you are still unsure what
> >is legal and was is not, go on the safe side and contact your
> >lawyer to get things straight.

Marc-Andre Lemburg
Y2000:                                                   144 days left
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