Issues with rtl_tcp

Adam Nielsen a.nielsen at
Thu Sep 27 00:12:37 UTC 2012

>> "Once this change is made in a given copy, it is irreversible
>> for that copy, so the ordinary GNU General Public License
>> applies to all subsequent copies and derivative works made
>> from that copy."
>> I am not a lawyer, but it seems to me that this statement
>> implicates that the library license is more restricted and
>> that things you are allowed to do under the library license
>> are still allowed under the general license.
> Clearly you're not. It's pretty much exactly the opposite actually.

I think you misread Leif's message - what was said is correct.  You can take 
an LGPL library and relicense it under the GPL, but you can't go back to LGPL 
again.  Yes, this implies the license becomes more restrictive, because there 
are things you can do under the LGPL that you can no longer do once it becomes 

> LGPL is _LESS_ restrictive and among those additional freedom, you can
> relicense it under GPL.

Yes, this is what Lief suggested.

>> This means you are free to use the rtlsdr dll available
>> at osmocom but you can not distribute an executable in
>> which the library is linked in.
> ??? How exactly did you go from taking a software distributed using
> GPL (rtl-sdr and librtlsdr) and just apply LGPL clauses to it ???
> As said above you can't do that at all.

I think what Leif was getting at is that you can do whatever you want if you 
don't distribute it.  The GPL and other licenses only come into effect once 
you distribute something to someone else.

> If you link to, you _have_ to be a GPL compatible license
> and that's it. That's how GPL works.

If I understand correctly, Leif was suggesting a workaround.  Instead of 
distributing something that violates the license, you could distribute 
something in two halves (each in compliance), along with instructions on how 
to link them together.  Once linked they can no longer be distributed, but 
because you were distributing them separately you wouldn't be violating any 

I'm not sure what the legal implications of this are.  On the one hand what 
you're distributing complies with the license, but then by providing 
instructions on how to link them together there is clear intent to bypass the 
restrictions imposed by the licenses.  I guess this is where advice from the 
SFLC comes in.


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