Written by Jamie Tanna
on May 12, 2026
CC-BY-NC-SA-4.0 Apache-2.0
3 mins

In the last month I've found I've been hyper aware of noticing folks writing open-source everywhere I look, which feels like there's something slightly larger at play.

Where I've had access and means to, I'll correct references to correctly call it either open source or Open Source as appropriate, but there's a lot out there I don't really have the time to try and correct for everyone, so here's a blog post to hopefully make more of an impact.

For those that aren't aware, there are two distinct definitions of these two capitalisations:

• Open Source: is reserved for an Open Source Initiative approved license, namely one that follows the Open Source Definition, which is a subset of all commonly used licenses
• open source: is anything else. There's no intake form, shared "official" definition that folks need to follow (which can cause issues), and so can include licenses like the Elastic License 2.0 (ELv2) or the Business Source License (BUSL), as well as the Hippocratic License

If this difference was news to you, congrats on being one of the lucky 10,000, and apologies that you're now going to start noticing inconsistent (and potentially incorrect) capitalisation everywhere!

Where possible, I try to be specific about whether I use Open Source or open source, and will refresh the readers' memory if I've not defined it yet. In the same vein, because there aren't many folks who understand open source or Open Source means that companies can get away with Openwashing, making folks think that the use of an open source license is great, when actually it's the Business Source License, or a case of "you can read the code but you can't contribute back".

Slide tangent aside, you'll notice that in neither of the capitalisations, open source nor Open Source are hyphenated. As the Open Source Initiative notes, Open Source is never hyphenated, and so for consistency, we should also follow the same for open source.

So why do I think there's been a rise recently of the incorrect hyphenation? Well, as every good Luddite, I blame the new technology!

I couldn't find - through a cursory search online - whether there's any recent research that's covered this, but it seems like Large Language Models (LLMs) are nudging folks to using the incorrect hyphenation of open-source.

I did a little research myself, using the following prompt, across a mix of models available to me:

what would you describe as the class of licenses like the MIT and GPL?

(Usual caveats about the non-determinism of responses)

As we can see, most of the models used are hyphenating, incorrectly, so it's more likely that folks who are using LLMs to help their writing, or who are talking about open source/Open Source will be getting nudged to wards hyphenating, incorrectly.

Words mean things, folks - be informed!