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Linking and the GPL (Technical and Legal Analysis)

I finally found a really useful working paper and law review article written by some European open source attorneys and the Free Software Foundation Europe on linking issues and the GPL license. I thought I would share some of the highlights with you as it is really hard to get some good practical guidance on open source legal issues. As a bonus, this perspective tries to marry the legal analysis with the technical analysis. Take a read!

(1) Derivative Work or Compilation (copyleft obligations)

Static Linking (GPL'd code combined with your code in one executable at build time)
Macro/Template Expansions (embedding GPL'd code into your code)

(2) Close Call (aka, it depends)

Plug-ins (to extend functionalities of other programs)
- depends on external factors (I added a few of my own here):
  - dependency/independency of your code;
  - communication protocols/sharing resources;
  - copying of API host code/no copying of API host code;
  - core functionality not subject to copyright/functionality subject to copyright; and
  - existence of other libraries with the same function.

(3) Independent and Separate Program (no copyleft obligations)

Dynamic Linking (calling and using library only at run-time; (no GPL code copied, modified, translated or changed . . . I added this part from Larry Rosen's view (see below) on it))
- remember to look at the above external factors as it could become a derivative work if the facts change
- oh yea, I moved Dynamic Linking to this section as I think it fits in here more than Close Call
Interprocess Communications (remote procedure calls)
System Calls (core operating system resources)
Interpreted Language 'Scripts' (not compiled, executed by interpreter, no third party code incorporated)

So long story short, this is an evolving issue and I don't think the definitive work has been written, but don't let that stand in your way of learning more about it. As an open source attorney and proprietary software attorney, I thought you should be aware of this, as these folks did a fantastic job with this working paper and law review article (see below).

Resources:

Working Paper on Software Interactions and the GNU Public License (July 2010)

Brian, Malcolm (2010) 'Software Interactions and the GNU Public License,' IFOSS L.Rev, 2(2), pp 165-80

Larry Rosen's view on Dynamic Linking.

Disclaimer: This post is for informational and educational purposes only, and is not legal advice. Hire an attorney if you need legal advice.