Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Tue, 18 Oct 2005 16:52:26 -0600

FWIW, despite your assurances, I do confess to remaining confused on this
matter due to the things that I read in the GPL FAQ. See below.

-- snip snip ---

If a library is released under the GPL (not the LGPL), does that mean that
any program which uses it has to be under the GPL?

    Yes, because the program as it is actually run includes the library.

What does it mean to say a license is "compatible with the GPL".

    It means that the other license and the GNU GPL are compatible; you can
combine code released under the other license with code released under the
GNU GPL in one larger program. The GPL permits such a combination provided
it is released under the GNU GPL. The other license is compatible with the
GPL if it permits this too.

What is the difference between "mere aggregation" and "combining two modules
into one program"?

    Mere aggregation of two programs means putting them side by side on the
same CD-ROM or hard disk. We use this term in the case where they are
separate programs, not parts of a single program. In this case, if one of
the programs is covered by the GPL, it has no effect on the other program.

    Combining two modules means connecting them together so that they form a
single larger program. If either part is covered by the GPL, the whole
combination must also be released under the GPL--if you can't, or won't, do
that, you may not combine them.

    What constitutes combining two parts into one program? This is a legal
question, which ultimately judges will decide. We believe that a proper
criterion depends both on the mechanism of communication (exec, pipes, rpc,
function calls within a shared address space, etc.) and the semantics of the
communication (what kinds of information are interchanged).

    If the modules are included in the same executable file, they are
definitely combined in one program. If modules are designed to run linked
together in a shared address space, that almost surely means combining them
into one program.

    By contrast, pipes, sockets and command-line arguments are communication
mechanisms normally used between two separate programs. So when they are
used for communication, the modules normally are separate programs. But if
the semantics of the communication are intimate enough, exchanging complex
internal data structures, that too could be a basis to consider the two
parts as combined into a larger program.

-- snip snip ---

Jeff

> -----Original Message-----
> From: Andrew Johnson [mailto:[email protected]]
> Sent: Tuesday, October 18, 2005 3:18 PM
> To: Jeff Hill
> Cc: [email protected]
> Subject: Re: FW: Ice GPL based Licensing
> 
> IMHO the GPL will only become a problem for EPICS if we include code
> that is licensed under it into the EPICS source that we distribute, at
> which point we *would* have to license EPICS under the GPL or at least
> explicitly dual-license it.
> 
> I don't know whether the EPICS license conflicts with the GPL or not,
> we'd have to get a lawyer involved to answer that question (although to
> my non-legal eye I don't see anything that would make the two
> incompatible).  If it doesn't then relicensing or dual-licensing EPICS
> under the GPL would be relatively simple; if it's not, we'd have to see
> whether the wording of the Grant of Licenses that we have from all
> contributors (other than APS and ANL) would permit us to relicense
> without additional permission, which I suspect it does.
> 
> However my main point is that as long as we distribute only our own
> source code, and we don't pull any GPL source code into what we
> distribute, then we're not breaking anyone else's license conditions.
> The combination of the ICE code and EPICS code would only happen at the
> end user site where the two get compiled and linked together, and the
> resulting binaries aren't usually distributed anyway.
> 
> Yes, there would be a problem for any commercial company selling
> something that includes EPICS+ICE binaries, but they're the one who
> would have to buy the commercial license for ICE, not us.
> 
> Note that John Sinclair is working on a QT-based version of EDM, and he
> has exactly the same problem since he's linking GPL'd Qt code against
> EPICS CA.  However as long as he distributes EDM as source code this
> isn't a problem at all and he doesn't need to worry about the
> compatibility of the EPICS license with the GPL.
> 
> - Andrew
> --
> English probably arose from Normans trying to pick up Saxon girls.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System