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.
(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: dependency/independency of your code, communication protocols/sharing resources, copying of API host code or not, whether core functionality is 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)
- 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.
Related Reading on Open Source
- AGPL: What Every SaaS Company Should Know About It
- 3 Things You Need in Your Open Source Policy
- What Software Companies Need to Know About the Creative Commons License Program
- A Software Lawyer’s Take on the Linux Foundation’s Open Compliance Program
Disclaimer:
This post is for informational and educational purposes only, and is not legal advice. Hire an attorney if you need legal advice.