Thanks to all those who commented on my recent proposal to "iconify" licenses. That is, representing the essential terms of various Free Software licenses as icons so you can quickly get a feel for their meaning. This is, in the current state of software licensing, no replacement for actually reading and understanding the licenses, but as a mechanism for quick (as opposed to deep) understanding it seems to work well enough.
ComputerDruid pointed out that we'd need an icon for the network-copyleft effect of the Affero-style licenses (AGPLv2 and AGPLv3). The salient point of the GNU Affero General Public Licenses is that the requirement to distribute source is also triggered by interacting with the program over a network. The license text has an addition (in version 3) to clause 13:
Notwithstanding any other provision of this License, if you modify the Program, your modified version must prominently offer all users interacting with it remotely through a computer network ... an opportunity to receive the Corresponding Source of your version ...
None of the licenses examined so far has such a clause, so that's why I hadn't drawn one up yet.
The "Free Software" icon is the only one that grants permissions. It says "this license grants you the Four Freedoms". The other icons all describe conditions on the license. Copyleft, network effect. The patent grant is both a permission outside the scope of copyright, as well as a condition related to downstream use of those patents and your own patent rights (if any) in the program (in those jurisdictions where there are software patents). In this sense, fewer icons means fewer conditions, and hence more free to use -- but at the cost of not guaranteeing the Four Freedoms downstream, for the most part. Compare, for instance:
This program is Free Software; you have at least the Four Freedoms, but copyright notices must be preserved and the license text distributed with the program.
This program is Free Software; you have at least the Four Freedoms, but copyright notices must be preserved and the license text distributed with the program. In addition, you are required to provide source (under some circumstances). The source provision applies to your own code as well that is added to the program (strong copyleft). The source provision applies also if you provide access to the program over a network (Affero). There is an explicit patent grant involved.
Whoo. That's quite some text, but still a great deal shorter than the GPLv3.
Paul Boddie points out that the "weak copyleft" symbol is probably redundant (I agree). That would make the number of source-related icons three (and the number of the counting shall be three). There would be "provide source" (i.e. weak-copyleft), and then two modifying icons for strong and network copyleft. I like it -- something to take into account in the wrap-up to this series.
See, by now we're almost getting into a grammar of these things, which is something I would like to avoid. Keep it simple, keep an overview that allows selection and understanding at a high level, and then look at the relevant license texts in detail.
So, let's move on to the license texts in detail for a moment. Yesterday I wrote up that the Apache license, version 2.0 and the Mozilla license, version 1.1 were roughly the same. Both got the same set of icons based on my quick reading of both licenses. So let's take a closer to see if there are relevant differences in the licenses. If there are, we may need to add a distinguishing badge.
General remarks: Apache has a notion of "contribution" spelled out in the license; I think this is intended to clear up what happens when you send a patch to a mailing list -- is that intended for inclusion under the same license or not? In my experience, people do submit patches that they do not want to have included -- on public mailing lists, no less -- but it is very rare. I don't think this is a crucial difference. The Apache license explicitly excludes linking as a means of creating a derivative work. The Mozilla license defines "commercial use" in a surprising way that includes many things I would consider non-commercial: namely, if I give my friend a USB stick with the source, that's commercial use according to the license. Mozilla has a concept of "Initial Developer", which I think is compatible with the Apache notion of "Licensor" -- they're both licenses that are directed at centralized projects with a clear central copyright holder.
Using the software: Mozilla clause 2.1a allows you to use, sublicense and distribute the code and modifications. Apache clause 2 allows the same, but makes explicit that object code distribution is allowed.
Patent grant: Mozilla clause 2.1b grants a license to those patents embodied in the Original Code. Mozilla excludes patents covered by code deleted from the original code -- so you can't re-implement something covered by a patent, it seems. Apache clause 3 does the patent grant and adds explicit termination conditions to that patent grant. Termination in Mozilla is covered in section 8.2. The termination in Apache applies to the relevant patents, while the Mozilla license terminates on any patent. That's an important distinction when it comes to litigation; I'm not sure it has a place in this iconic scheme, though.
Trademarks: Neither (software, copyright) license grants a trademark license. Apache makes this explicit.
Distribution: Mozilla clause 3.1 and Apache clause 4.1 both require distributing the license text. Both require a notice of modifications made to the original source, but Mozilla wants that in a separate file while Apache allows you to annotate the files themselves. This is similar to the GPLv2 clause 2a, and is something that I very rarely see people (or Free Software projects) do systematically. I don't think it's a crucial difference.
Copyleft: Ha, I'm such a moron. How could I have missed this? See, Mozilla clause 3.1 and 3.2 say that the Mozilla license applies to the source code and that the source must be available, also for modified versions. While you may distribute executables under a different license, they must have corresponding source code available under the Mozilla license. So that's a copyleft license, and the source for executables is available. But ... and this is a pretty darn big but ... the Apache license does not require this. Clause 4 says a number of things about distribution as source, and allows distribution in object form, but places no restrictions on the distribution of object forms except that the license needs to be included. In other words, you can use the Apache license and distribute binaries without providing source. With Mozilla, you can't.
So it's a good thing that the similarity in the reduced representations of the licenses (i.e. the row of icons) has led to a re-examination of the licenses, because it leads to the understanding that the licenses are not the same, by a long shot. Of course, I could have just looked it up in the FSF license list: Mozilla (copyleft, not GPL compatible) and Apache (no copyleft, GPL compatible). If I were a professor I'd claim I'd made the error intentionally in order to spur closer examination of both licenses.
Tomorrow I'll carry on with the next 10 licenses in the top-20 list to see if any interesting new features show up, and then on Saturday I can wrap up with a table showing the 10-mile view of all those licenses.