Non-FSF Copyleft Usage (24 Mar 2021)

The Free Software Foundation has decided they'd rather hang out with a sex pest than have an ounce of credibility, so fuck em. Let's look at the copyleft licenses they didn't write and see how they're used.

I'll be using the Blue Oak Council's list of copyleft licenses here, because I don't know of a good other way to find specifically copyleft licenses. I'll be searching GitHub for filename:LICENSE "<some snippet from the license>" or checking Wikipedia and then seeing if anything notable turns up.

Maximal Copyleft

• Cryptographic Autonomy License: almost entirely cryptocurrency bullshit
• Parity Public License: maintains its own list of users, including some work from substack (original author of browserify, prominent in the node.js scene, name stolen by a shitty newsletter startup) and some Git hook manager with 22.2k stars on GitHub (although it's only Parity licensed while it's in early access, and it'll revert to MIT later on). so there's a notable person and a notable project using this license, which is neat.
• Reciprocal Public License: well, there's "the most popular service bus for .NET", but that appears to be basically it.

Network Copyleft

• Affero GPL: fuck GNU, fuck the FSF, fuck RMS, fuck you
• Apple Public Source License: unsurprisingly, the only use I've seen is for stuff derived directly from Apple releases
• Common Public Attribution License: apparently it was invented by some startup that hasn't existed since 2012, and I could only find one nontrivial use of it
• European Union Public License: well, there's "dig but i rewrote it in rust" and there's Pi-hole (actually neat!) but that's about it. i think being the pi-hole license (plus having a metagovernment behind it) would probably be enough to ensure its longevity.
• Non-Profit Open Software License: GitHub can't find any usage of it!
• Open Software License: it's got Magento (WordPress for ecommerce) and that's about it
• RealNetworks Public Source License: ehhhhh I am officially ignoring any license with a mostly-defunct vendor in the title now

Strong Copyleft

• BSD Protection: nothing uses this
• CC BY-SA: that's not a software license, you can't fool me
• GPL: fuck that
• Q Public License: this name has aged poorly and i can't find use of it
• Sleepycat License: adorable! but not used by anything

Weak Copyleft

• Common Development and Distribution License: apparently this is popular with enterprisey bullshit because it started at Sun but it seems like it's mostly enterprisey bullshit
• Common Public License: this one's IBM's, so there's even less usage
• Eclipse Public License: well, there's Eclipse, but also a lot of other non-enterprise-bullshit (mostly Java) stuff apparently
• Erlang Public License: even Erlang doesn't use it anymore lol
• IBM Public License: ehhhhhhhh
• LGPL: fuck that
• Mozilla Public License: lots of users, probably not going anywhere anytime soon
• Microsoft Reciprocal License: not really widely used, unsurprisingly
• Sun Public License: apparently it's the older, worse CDDL

Summary

for maximal copyleft ("must publish source, even if only changing for internal use"), Parity is probably the most promising future license.

for network copyleft ("must offer source to users even across a network"), the European Union Public License is already seeing some adoption.

for "strong" copyleft ("must offer source to users even if just linking as a library"), there are no good options because the GPL has been the only game in town for ages.

for "weak" copyleft ("must offer source to users"), the Mozilla Public License looks like it has a good chance of continuing to exist and be used by actual projeccts for a nice long while.