Skip to main content.
home | support | download

Back to List Archive

Re: DLL and license

From: Luke Ross <lukeross(at)>
Date: Thu Jun 27 2002 - 11:27:57 GMT

Patrik Hrkut wrote:

>we are using Swish-e in our Intranet and we are very satisfied with it. We want 
>to use Swish-e also on our commercial CD as search engine. We were looking for
>an DLL library for Swish-e in Internet, but we didn't successful. (Does somebody
>know about existence of such DLL ? ) 
>Now we will try to make own Swish-e DLL. And the question is: 
>When we make an DLL and we use it on our CD in other application (front-end to
>swish-e), should we publish the whole application under GPL, or only the DLL ? 
>Or when we call swish-e.exe (supposing we won't be successful in making DLL )
>from the front-end also the whole application should be pubished under GPL ?
I'm not a lawyer, so I'm not promising this is correct.  The GPL FAQ says:


        I'd like to incorporate GPL-covered software in my proprietary
        system. Can I do this?

You cannot incorporate GPL-covered software in a proprietary system. The 
goal of the GPL is to grant everyone the freedom to copy, redistribute, 
understand, and modify a program. If you could incorporate GPL-covered 
software into a non-free system, it would have the effect of making the 
GPL-covered software non-free too.

A system incorporating a GPL-covered program is an extended version of 
that program. The GPL says that any extended version of the program must 
be released under the GPL if it is released at all. This is for two 
reasons: to make sure that users who get the software get the freedom 
they should have, and to encourage people to give back improvements that 
they make.

However, in many cases you can distribute the GPL-covered software 
alongside your proprietary system. To do this validly, you must make 
sure that the free and non-free programs communicate at arms length, 
that they are not combined in a way that would make them effectively a 
single program.

The difference between this and "incorporating" the GPL-covered software 
is partly a matter of substance and partly form. The substantive part is 
this: if the two programs are combined so that they become effectively 
two parts of one program, then you can't treat them as two separate 
programs. So the GPL has to cover the whole thing.

If the two programs remain well separated, like the compiler and the 
kernel, or like an editor and a shell, then you can treat them as two 
separate programs--but you have to do it properly. The issue is simply 
one of form: how you describe what you are doing. Why do we care about 
this? Because we want to make sure the users clearly understand the free 
status of the GPL-covered software in the collection.

If people were to distribute GPL-covered software calling it "part of" a 
system that users know is partly proprietary, users might be uncertain 
of their rights regarding the GPL-covered software. But if they know 
that what they have received is a free program plus another program, 
side by side, their rights will be clear.

My interpretation of this is that a DLL is a seperate bit of software 
effectively, communicating at 'arms length' (the DLL calls).  I'd say 
you'd have to release the DLL under the GPL, and release the main 
program under a differerent license, as long as everything relating to 
Swish-E is solely in the DLL.

Received on Thu Jun 27 11:31:30 2002