> I prefer to think of the distinction in this way: permissive licenses provide the maximum freedom for downstream developers (including the ability to use the open source code in a closed source project), whereas copyleft licenses provide the maximum freedom for downstream users.<p>This is a common analogy but it never sits well with me. Really, the permissive licenses allow the code to show up in places that copyleft licenses would not allow it. There are a ton of open source projects used in Microsoft Windows or iOS thanks to their permissive licensing -- and neither Microsoft nor Apple are legally obliged to give anything back.<p>Copyleft licenses prevent the software from being forked into a proprietary program and the changes hidden from the user. To take a random example, if Microsoft took GNU gzip and included it with Windows, and then extended it with new features, Microsoft would be obliged to provide the source code to those changes. If they took OpenBSD's implementation instead, they wouldn't be obliged in the same way (though they still _could_).<p>Remaining entirely in the open source world, these licenses concern redistribution of software. A user on OpenBSD does not feel they have any less freedom than a user on GNU/Linux. They don't have any less freedom, after all. Users on both systems retain the full gamut of freedom. To run for any purpose, to study the source code, to modify the source code, to redistribute the software verbatim or modified. The difference shows up when it comes to this: Do you want to be an asshole? OpenBSD permits the option -- you can distribute a fork without the source code. You cannot do that with a GPL-licensed system.<p>The FSF and other GPL advocates usually ride on the premise that opening up the possibility for downstreams to be assholes is bad, with few exceptions. I do respect their opinions, but I feel like the history of open source (and the *BSDs, even) show that such assholes don't get very far. They simply cannot compete with the pace of open and transparent development and die off on their own. Frankly, being an asshole is an irrational and unprofitable (socially and commercially) move, and trying to nanny the behavior away isn't all that necessary.
Those who wish to learn more about copyleft after reading Ben's article may also want to look at the copyleft guide <a href="https://copyleft.org/guide" rel="nofollow">https://copyleft.org/guide</a> for more information.<p>Ben is a contributor to the copyleft guide, so we'll likely merge in his article into the Guide.
Discussions of copyleft versus permissive licensing always seem to cover the same “freedom for users versus freedom for developers” clichés and the same tired slavery metaphors.<p>My dislike of copyleft is emphatically not because I want to enable proprietary software. I hate proprietary software, and don’t use it on my machines.<p>No, my biggest complaint about copyleft has always been that it prevents <i>other free software</i> from being able to use it. Copyleft licenses actively lead to incompatibility.<p>Remember when LibreDWG, an AutoCAD file parser, couldn’t be used in various free software CAD projects, because LibreDWG is GPLv3+ and FreeCAD, etc were GPLv2 only? <a href="http://libregraphicsworld.org/blog/entry/libredwg-drama-the-end-or-the-new-beginning" rel="nofollow">http://libregraphicsworld.org/blog/entry/libredwg-drama-the-...</a><p>If FreeCAD had been under a permissive license, it would have been able to link against LibreDWG. If LibreDWG had been under a permissive license, FreeCAD would have been able to link against it. If they were <i>both</i> under a permissive license, they would have been able to be linked together <i>and</i> share code directly!<p>How about when NYC released open building and address data? A laudable move, one that helped several open source projects, the largest probably being OpenStreetMap. OpenStreetMap is under a copyleft license, and though they benefit from NYC’s data, due to the licensing NYC can’t make use of OpenStreetMap’s improvements without a convoluted parallel construction scheme: <a href="https://www.openstreetmap.org/user/lxbarth/diary/23588" rel="nofollow">https://www.openstreetmap.org/user/lxbarth/diary/23588</a><p>A common response is that the onus is on NYC to release their data under a copyleft license so they can benefit. But there are often significant (even legislative!) barriers to doing that, especially in the United States where government entities are often required to release data to the public domain. How about changing that legislation? Well, if you had initiated such a legislative reform just a few years ago OSM would have been under the Creative Commons BY-SA—which is incompatible with OSM’s current license, the ODbL.<p>Remember how much grief has resulted from the unclear (or perhaps too clear) licensing status of ZFS on Linux?<p>Releasing software and data under the freest, most permissive license possible prevents such a thing from ever happening. I would rather allow a hundred Chinese featurephone vendors to lock down their crappy derivatives of my code than use my copyright to prevent a free software project from using my code in good faith.
Can you make money writing and selling copyleft-licensed software? The licenses always appeared to me to make that difficult. I write one, sell it, and the purchaser can now give it away for free. But I probably just don't understand it.
"Permissive" licenses provide highest freedom to "distributors".<p>"Copyleft" licenses provide highest freedom to "end-users".<p>"distributors" normally tend to be corporations that want to benefit from "free" software, but OTOH deny the same freedom to their own users. In other words, software that uses free software internally, but it itself was a proprietary with stringent license terms.
I think the best explanation of the differences between Free Software, Open Source, and Copy Left is the first 30 minutes of Revolution OS.<p>This part for copyleft, does anyone really find this difficult to understand?<p><a href="https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s" rel="nofollow">https://www.youtube.com/watch?v=k84FMc1GF8M&t=17m13s</a>