The GPL License

Community Forums/General Help/The GPL License

col(Posted 2013) [#1]
Hiya,

I'm thinking of using a piece of software thats covered by the GPL license. I won't pretend to fully understand the legal issues using it so I'm asking for a little help from some experienced people... here :-)

My software will call the GPL covered exe externally from my source - it's not included within my source at all.

My questions are...

Does the GPL license mean someone has the right to ask for the source code for the GPL covered software? And as my software is calling the GPL covered exe does that then mean that my software has to be GPL licensed too? meaning that someone has the right to ask for my source code too?

EDIT:- I understand this may or may not be enough information to give a concise answer, so please forgive me for any points that may be important that I have missed out. If you need more information then tell me and I'll provide.

Cheers!


col(Posted 2013) [#2]
...


Iowalien(Posted 2013) [#3]
yes yes & yes


Yasha(Posted 2013) [#4]
My software will call the GPL covered exe externally from my source - it's not included within my source at all.


As long as this is the case, it's "yes", "no", "no". If you don't actually provide the GPL program yourself but make the user retrieve it themselves from a third-party location, then you don't need to provide source to that either since it stops being your problem.

Calling an exe is not linking, and your own program wouldn't be considered a derivative work at all. Just one program using another.

The second you do anything more involved than just calling the program with arguments though, it becomes a different matter. Any kind of binary linking turns your program into a derivative work.


col(Posted 2013) [#5]
Thanks Yasha,

That makes sense.

One note is that I would be supplying the GPL covered exe with my application. I understand that I need to include the GPL license information that covers it, however do you know if its acceptable to include a link to the source or will I have to include the source with my distribution or is it ok that I keep a copy of the source that I can present should anyone request it?

Thanks!


Kryzon(Posted 2013) [#6]
If you use a GPL library in DLL form, do you still need to supply the source to your program?


Yasha(Posted 2013) [#7]
however do you know if its acceptable to include a link to the source or will I have to include the source with my distribution or is it ok that I keep a copy of the source that I can present should anyone request it?


Here are the corresponding answers in the GPL FAQ:
http://www.gnu.org/licenses/gpl-faq.html#UnchangedJustBinary
http://www.gnu.org/licenses/gpl-faq.html#AnonFTPAndSendSources

i.e. Link is good, but it should be to your own copy on a server/storage you control (basically because you're not supposed to offload this responsibility once you've taken responsibility for the binary). Sources need to be just as easy to get as binary, so you aren't supposed to make people request sources manually if they were able to download the binary directly.


If you use a GPL library in DLL form, do you still need to supply the source to your program?


This one is directly answered here: http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL

i.e. yes. Intuitively speaking this is the major difference between the GPL and LGPL. (There are probably edge cases. Don't rely on them.)

Note that there's also such a thing as "GPL with linking exception", so for instance all MinGW programs include GPL'd code (the C runtime), but it has a special exemption on it. This needs to be spelled out explicitly.

There's also a wider-case point of view: http://www.gnu.org/licenses/gpl-faq.html#NFUseGPLPlugins ...which basically amounts to "don't try to outwit the GPL".

At any rate if someone's placed a DLL under the GPL their intention is pretty clear: they don't want you to use it with a non-GPL program.


Most important thing though: certainly for a commercial project it's a really bad idea to release anything unless you fully understand the legal implications of what you're doing. If you still don't understand the text of the licence itself after looking at the FAQ or forum discussions, consider either hiring a lawyer or just using different software with a simpler licence.


col(Posted 2013) [#8]
Thanks again, yourself and the links provide the information I needed.

Cheers!