GPL License

[mikecarr]

We are considering the Windows binary version of ExifTool for use as a component in a commercial application. For our purposes the Perl license is entirely acceptable, however we noticed that  code in  BZZ.pm (Image::ExifTool::BZZ) is based on BSByteStream.cpp of DjVuLibre 3.5.21 which carries the GPL license. DjVuLibre-3.5 is itself derived from from the DjVu(r) Reference Library from Lizardtech Software which is also GPL licensed.

Can you please confirm whether or not the authors of BSByteStream.cpp gave there permission for use of their code under the Perl license? If not, is there an alternative to BZZ.pm avaialble?


Regards

Mike Carr

[Phil Harvey]

Hi Mike,

I didn't realize that the GPL was more restrictive than the Perl Artistic license.  If GPL is a problem for you, perhaps I should just drop the BZZ module (and hence DjVu support) from the Windows binary.  My goal is for ExifTool to be free.

- Phil

[Alan Clifford]

I thought the basis of the GPL was that it insisted it was all for free.  So if you use GPL code, you have to make your source code available as well.  People don't like it and call it the GPL virus because they want to use the free source code but selfishly not make their own derivations available for free.

[Phil Harvey]

The ExifTool source code is free, so it conforms to this GPL license.  And I would be surprised if the GPL license restricted you from executing a GPL application from a commercial application.  I am assuming that the intended purpose is to run exiftool.exe, not to combine the ExifTool source code into the application.  If running the .exe was a problem, then one couldn't execute a system command from any application on a GPL system, which doesn't make sense.  Perhaps the only difference is that ExifTool would be bundled with this application.  But again, this restriction would be stupid because you could get around it by simply having your application download and install ExifTool itself.  So I don't get it.

But I haven't studied the GPL license, and I'm not a laywer, so what do I know?

- Phil

[Phil Harvey]

OK, I read the GPL2 license.

The way I read it, a commercial application may include the ExifTool application in its distribution provided that it:

1) Conspicuously displays the appropriate copyright notices.

2) Provides a link to where the ExifTool source code may be obtained.

I believe that these requirements are similar to those of the Perl Artistic license.

So if there is a problem, I don't see it.

- Phil

[mikecarr]

Phil

Thanks for your responses. We are working with a lawyer who is particularly "risk averse". Like you I don't believe there is really a problem as the app doesn't link to ExifTool (Windows Binary) but runs it and redirects the output but I had to ask the question.
Re-compiling without BZZ is an option.

So far we've found ExifTool to be excellent and comprehensive in coverage so we're grateful it.

Mike