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Open Source Licences Wars - Revision 2

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Revision History
Revision 265921 August 2009shlomif
Fixed some small typos and misphrasings.
Revision 265121 August 2009shlomif
Added descriptions of strong copyleft licences, some links to opinions about which licence to choose. Spell checked and prepared for release.
Revision 245330 June 2009shlomif
Added descriptions of weak copyleft licences.
Revision 245230 June 2009shlomif
Fixed some typos and misphrasings.
Revision 243418 June 2009shlomif
Added the Freecell though experiment.
Revision 243318 June 2009shlomif
Added the Exceed thought-experiment.
Revision 243118 June 2009shlomif
Added the part about the GPL and the hacker attitude.
Revision 242815 June 2009shlomif
Finished up to the first E-mail in the Hackers-IL thread. Now to cover the rest of the E-mails.
Revision 100019 July 2008shlomif
Forked the template from a previous work and working on it.


Discussion and comparison of free and open source software licences.

Table of Contents

Types of Licences
What is a Free Software Licence?
Public Domain Licences
Weak Copyleft Licences
Strong Copyleft Licences
Uncertainty in Categorising Licences
Some Opinions about the Different Licences
Which Licence To Choose
Bad Idea No. 1: Choose a non-Open-Source Licence
Bad Idea No. 2: Choose a non-GPL-Compatible Licence
Bad Idea No. 3: Choose a Custom Licence
Bad Idea No. 4: “Same Terms as Perl”
Bad Idea No. 5: Under the Public Domain
Bad Idea No. 6: Using the GPL or the LGPL
Why I Prefer the MIT X11 Licence
Strong Copyleft and Preventing Threats to FOSS


When Joel Spolsky (“Joel on Software”) wrote his notorious blog post “Language Wars”, many people asked whether he has “jumped the shark” and that his blog will go downhill from there. I too have read the post, and agreed, that while it had a few good points, it was too based on “feeling rather than knowing”. Joel later on posted many good articles and shorter entries on his blog, but many people still recalled it as a very low-point in the blog.

Like Joel, I have a home-site and several blogs, where I post articles and essays about my thoughts, and this time I’ve decided to risk something similar to what Joel has done on an equally flamatory topic: licences of open-source software. I’m going to introduce the various options, explain a little about their motivation and then give some advice according to my own personal opinion.

I should note that I am not a lawyer, and only write this according to my best knowledge, understanding and experience. [IANAL] I think what I’m writing here is correct, but would still appreciate any correction for future versions. If you’re unsure about my advice, then you should consult a legal expert (if you can afford one) or your local or global Free and Open Source Software organisation. I cannot guarantee my advice is valid.


In this spoiler I’ll explain what I’m using right away, which is also what I recommend other people to use. When I started releasing my code as open-source software, I used the Public Domain. So, for example, Freecell Solver which is one of my earliest projects and still one of the most successful, used to carry a COPYING file with the following contents:

Relax, this is not GPL software, but rather it is distributed under the public domain. It means it can be linked against anything, converted to any different license, freely used and distributed, and anything else without any restrictions whatsoever. No Strings Attached!™

(This was also a joke of sorts.)

Later on, to avoid the problematic status of public domain code in many countries, and to avoid other potential legal problems, I started distributing my original code under the MIT X11 Licence, a BSD-style licence which is the closest one to the Public Domain. If the project I’m contributing to has a different licence, then I disclaim any explicit or implicit ownership on the code I wrote, and allow the existing copyright holders to do with my code as they see fit.

Note that I’m using different terms for other types of digital artworks. Most of my essays (including this one) are under the Creative Commons Attribution Licence, my original (i.e: non-derived-work or fan-art) fictitious stories are under the Creative Commons Attribution-Share Alike Licence (which is more GPL-like), and most of the photos I took and published were placed under the Public Domain.

[IANAL] Some people believe that discussing legal matters should be reserved to people who are Law experts. However, this is a sub-case of the “only specialists should deal with a specialised field” fallacy.

Like it or not, the Law affects us all and the Government expects common citizens to be aware of it and not violate it, even if they are not lawyers. As software developers, we do not limit discussions on software and computing to people with a Bachelor’s degree in Computer Science (much less a Ph.D. or whatever) and often not-too-qualified people can be very knowledgeable and/or productive.

Similarly, I expect discussions on the governmental law to have a lower barrier for entry than people who are qualified lawyers, or Law Professors.