[tlug] non-GPL dll inside GPL

["Stephen J. Turnbull" <stephen@example.com>]

Nguyen Vu Hung writes:

 > Unikey ( http://unikey.org ) is a Vietnamese keyboard driver licensed
 > under GPL.

 > Arcording to README.txt in Unikey 3.62, it contains a non-open-source
 > library ( rtfio.dll ).

 > The author is the same guy and he releases Unikey under *GPL*

No problem for *him*, as long as he is sole author.  (Equivalently, he
has received assignments of copyright to contributed code, or
appropriate licenses from contributors.)  Copyright holder can do
anything he wants to.

There is a problem for recipients who wish to share, however, in that
unless he gives specific permission to redistribute Unikey without
source to rtfio.dll, they are at risk of being sued by him for doing
so.  I suppose he would lose in a U.S. court, but why risk it?  And I
have no idea what a Vietnamese court would think, since I guess
Vietnamese law derives from the French system.

The exception for system libraries in the GPL itself is in principle
similar.  Note that the exception is explicit there.  The author of
Unikey should do the same thing.

There is also a problem of reverse engineering rtfio.dll.  Is it
permitted?  Almost certainly not.  How about writing a plug-compatible
library to that interface?  I think so, but how does the author feel?

The simple approach would be to license Unikey under the LGPL, and
note in the permissions notice that rtfio.dll, and perhaps rtfio.lib
and intrtfio.h, are not part of Unikey.

The author may prefer to clarify his intentions with an explicit
permissions notice.  For example

    Unikey is free software.

    You may copy, modify, and redistribute Unikey under the conditions
    of the GNU General Public license.  As a special exception you
    need not provide the source code to the libraries rtfio.dll and
    rtfio.lib.

    The three files rtfio.dll, rtfio.lib, and intrtfio.h are not part
    of Unikey, and are not free software.  If you redistribute them,
    they must be redistributed as verbatim copies.  You may not
    redistribute them in any other way.  Furthermore, no permission is
    granted to reverse engineer the rtfio library code.

Note that the author may feel differently about rtfio.lib and
intrtfio.h, and be willing to let people change them, I'm just
guessing about what he might want.

This would probably piss off rms, though, and may violate clause 6 of
GPLv2.  And I'm pretty sure it's not compatible with GPLv3, which is
very specific about what additional terms and conditions may be added
as riders.  He probably ought to check with a lawyer.