corridorkey's questionable open-sourceness

or, how not to license software

recently, corridor digital released an “open source” chroma keyer which uses machine learning. i was immediately intrigued, because this is exactly what we should be using “ai” for: tasks that are too advanced for a mere algorithm but too tedious for a human to want to do. in my excitement i took a look at the repo, and… oh god. not only is the most prolific contributer anthropic’s claude github account, but the “corridor key license” is a barely modified copy of the creative commons attribution-noncommercial-sharealike 4.0 international public license, or cc by-nc-sa 4.0. let’s take this one step at a time, shall we?

part 1: vibe coding

i don’t want to dwell on this for too long because franky i’m tired of bitching about it. releasing code to the public that you didn’t write and don’t have to knowhow to understand isn’t just stupid and insulting, it’s unsafe. if you insist on vibe coding, vibe code at your own peril, not to the detriment of others. don’t release anything written by an ai that you don’t understand. you may be accidentally publishing malware, or at the very least a messy codebase that you have no idea how to maintain. anyway…

part 2: what the hell is creative commons?

creative commons is a collection of licenses for creative works, basically anything you could consider “art”. drawings, animations, music, videos, most things. it ranges from cc0, which is basically just public domain, all the way up to the most restrictive cc by-nc-cd. i won’t bore you with the specifics, but it’s worth keeping in mind that, while a cc license can be restrictive in some ways, you are always permitted to “copy and redistribute the material in any medium or format”. now, what the hell is a lesson about creative commons doing in an article about software? well…

part 3: creative commons is not a code license

they explicitly tell you this. software licenses, aside from public domain, basically MUST be separate from the licenses given to creative works. there’s a reason github doesn’t let you pick anything but cc0 when you make a new repo. i don’t know how to describe why without just straight up telling you the things that will go wrong if you ignore this warning.

by means “attribution”, which means credit must be given to the creator alongside any work that distributes, remixes, adapts, or builds upon the material in any form. this is fair and i feel like most people would do this just out of courtesy even if not required to. but here’s where it gets spicy!

nc means “non-commercial”, which means only non-commercial uses of the work are permitted. if you’re at all familiar with software licenses, you’re right to be confused about why this might be a problem. a bunch of software licenses are non-commercial! how many times have you installed a program which says “if you paid for this, demand a refund!”? the problem is that creative commons is not a code license. normally, a piece of software being non-commercial doesn’t matter for a creative work because software licenses are specifically for software, which means “non-commerial” would be for the program, not works created with the program. this is obviously a huge problem for a tool which chroma keys videos, because people like to make money from their art, either by selling it or running ads on it, and the non-commercial element of this license prohibits that. “well whatever, i can just sell it anyway, right? fuck copyright law!”, right? wrong.

sa means “sharealike”, which is sometimes referred to as “virality”. this is a core defining feature of version 3 of the gnu gpl, a ludicrously popular license from the free software foundation which refers to itself as “copyleft”. so if this is normal in software, what’s the problem? well, i remind you, creative commons is not a code license. normally, if you use gpl code, your project must also be gpl. simple, it prevents what is referred to as “tivoization”. however, since creative commons is meant for creative works, not code, it’s completely unclear how this would affect a piece of media that makes use of the program. does the sharealike clause apply to the video file rendered by the program? there’s no precedent for this to my knowledge, and the license doesn’t clarify. at best, it’s a legal grey area. at worst, it can be assumed that work that makes use of a cc sa licensed program must be shared under the same terms. this is, in a manner of speaking, REALLY FUCKING BAD.

part 4: summary

or, i’m too lazy to read allat

to summarise, what exactly would happen if i, say, made an independent movie using corridorkey? well…

1. i would need to credit corridor for my use of corridorkey. fair enough!
2. i am not allowed to monetise my movie in any way, not by running ads on it, not by selling it, nothing.
3. my movie becomes cc by-nc-sa, which means even if i ignored the non-commercial aspect and sold my movie anyway, the buyer of said movie has the full legal right to distribute copies of it for free in any way they please to anyone they please, including putting it up for free download on the internet. if i attempt to take this pirate to court, i will lose, because in the eyes of the law, my movie is free to share.

if you are making anything that makes use of a chroma keyer, look somewhere else. i’ve seen the results this program can help make, and they do look frankly incredible, but if you have any intention of retaining the copyright of your own work either because you wish to monetise it or because you wish to release it to public domain or under your own set of restrictions, avoid this program for the time being. if you’re anything close to a serious creator, i would treat this repo as “look but don’t touch” until further notice. i’m happy to update this post if they reconsider the license choice! maybe gpl v3 or lgpl v3, since they align closely with cc by-nc-sa, but are specific to software? choosealicense.com

do research. don’t code with llms. thanks for reading.