

Ask HN: What are the differences between the major free software licenses? - LearnYouALisp

This has been a recurring question. Where can I learn about the differences between commonly used licenses (MIT license, BSD, GNU GPL, and so on) in a clear way?<p>I've taken a look at the actual statements, and they were not as daunting as I had supposed. However, it is still a little difficult and time-consuming to process the unfamiliar clauses, translating them into normal English and simplifying them into basic points. Do you know of a website or guide that has done this already?<p>Update: I have found the following chart, but it only gives two items: "Link with code using a different license", and "Release changes under a different license".<p>http://en.wikipedia.org/wiki/Comparison_of_free_software_licenses
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JoshTriplett
First of all, let me start with the disclaimer that no summary substitutes for
reading the licenses in question. The MIT and BSD licenses require almost no
effort to understand. The GPL (v2 or v3) makes for fairly easy reading, and
seems intentionally written in a way that non-lawyers can easily understand
and apply. The same mostly goes for the LGPL and Apache licenses, though the
use cases for the latter don't become immediately evident at first glance.

For a quick overview of the most popular licenses, I really like this diagram:
[http://paulmillr.com/posts/simple-description-of-popular-
sof...](http://paulmillr.com/posts/simple-description-of-popular-software-
licenses/)

That diagram rather effectively captures the most important differences
between the licenses: copyleft of various strengths (GPL versus LGPL versus
BSD/MIT), the added protections in the GPLv3 and LGPLv3 versus the v2
licenses, the rationale for the Apache license rather than MIT/BSD, and the
subtle difference between BSD3 and BSD2 that you mostly don't need to care
about.

If you want a more extensive analysis, I'd suggest reading the FSF's license
list, which provides a rather comprehensive list, including specific issues
with various licenses, and links to more information about common license
features: <https://www.gnu.org/licenses/license-list.html>

One critically important disclaimer about that list: ignore _everything_ it
says about the GFDL (GNU "Free" Documentation License) and stay _far_ away
from that license. Always license your documentation under the same license as
your code; don't use a separate, incompatible license.

You may also find the rather extensive and provocatively titled essay "Make
your Open Source Software GPL-Compatible or Else" useful:
[http://web.archive.org/web/20110718154125/http://www.dwheele...](http://web.archive.org/web/20110718154125/http://www.dwheeler.com/essays/gpl-
compatible.html) . (Link to the Internet Archive because dwheeler.com seems
down at the moment.)

Hope that helps.

~~~
LearnYouALisp
Could you explain what you mean by this, please?

> ...Ignore everything it says about the GFDL (GNU "Free" Documentation
> License) and stay far away from that license. Always license your
> documentation under the same license as your code; don't use a separate,
> incompatible license.

I am about to open the essay you gave a link to. Also, for those interested,
here is the discussion linked below the diagram:

<http://news.ycombinator.com/item?id=2501536>

~~~
JoshTriplett
Sure, happy to elaborate on that.

The GNU project repeatedly talks about documentation and other works as
somehow separate from software, and makes comments like this: "However, for
manuals and textbooks, or more generally any sort of work that is meant to
teach a subject, we recommend using the GFDL rather than the GPL.". See this
FAQ entry for a more extensive example: [https://www.gnu.org/licenses/gpl-
faq.html#WhyNotGPLForManual...](https://www.gnu.org/licenses/gpl-
faq.html#WhyNotGPLForManuals) . (Disclaimer again: I disagree entirely with
just about everything said in that entry, as do numerous other FOSS
developers.)

In general, the GNU project doesn't care much about things other than
software. In particular, they've said they don't care much about the ability
to modify data (such as media for a game), and they actively oppose
modifiability of non-technical writing (such as their own essays, which allow
unmodified copies only).

Among other things, the GFDL allows manuals to contain extensive unremovable
and unmodifiable sections, such as the GNU Manifesto (which many people mostly
agree with and find inspiring) and "Free Software Needs Free Documentation"
(which many people strongly disagree with due to it propagating many of the
same advocacy of the GFDL). The GFDL also contains very particular
requirements about text placed on the front and back covers of a printed book
(beyond just attribution), which also does not permit modification. (That
requirement seems particularly hypocritical given the FSF's own essay about
the GPL-incompatible 4-clause BSD license with advertising clause,
<https://www.gnu.org/philosophy/bsd.html> .)

Most importantly, the GFDL and GPL remain incompatible licenses, which means
you can't copy anything between documentation and code.

All of the above contributes to my recommendation that you ignore anything the
GNU project says about the GFDL, and anything they say about not using the GPL
on manuals.

All that said, I do actually consider almost all of the GNU project's
"philosophy" section (<https://www.gnu.org/philosophy/>) well worth reading;
it certainly inspired me when I first started learning about Free Software.
Just take some of it with a grain of salt, particularly when it comes to
anything other than software, because the GNU project really doesn't care
about anything other than software.

Fortunately, the most recent update to the GFDL provided a way for Wikipedia
and other large wikis to transition away from the GFDL and to the Creative
Commons Attribution Share-Alike (by-sa) license, which doesn't have the issues
with Invariant Sections and Cover Texts. Creative Commons licenses remain GPL-
incompatible, which can cause practical problems for anything that might mix
with other FOSS work, but not for Wikipedia and other similar wikis. Many
people avoid them for software documentation for that reason, but they seem
like perfectly reasonable licenses for almost any other work.

Recommendations for non-software: For documentation or other bits associated
with a software project, use the same license as that software project. (For
instance, X11 documentation uses the all-permissive MIT license, and the
documentation for most non-GNU GPLed projects uses the GPL.) For any other
work, use the GPL if some clearly identifiable "source" form exists that you
want to preserve access to, use CC-by-sa if not but you still want a copyleft,
and use CC-by or a simple all-permissive license like MIT otherwise.

~~~
LearnYouALisp
That is a lot to take in, thank you for another extensive response.

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LearnYouALisp
This seems to have died out very quickly without any visibility.

