The README states that this software is licensed under that license.

That page, has a notice. Here it is in full:

This license was applied to software published by W3C before 13 May, 2015. On 13 May, 2015, W3C adopted a revised and renamed "software and document" license and applied the new license to all W3C documents that had previously been made available under this license. The new license grants all permissions that had been granted under this 2002 license.

There are two parts in particular that are relevant here:

This license was applied to software published by W3C before 13 May, 2015.

This software is older than me, so that timeline checks out. It also totally makes sense to use a new license for new projects.

But this:

On 13 May, 2015, W3C [...] applied the new license to all W3C documents that had previously been made available under this license.

This sounds like it implies that this software is now licensed under a new license (and actually relicensed again in 2022, due to the notice on the 2015 license)

I'm not sure it's valid to do so? Does the W3C have the copyright to all code in this software? There are only 17 code contributors, so maybe they all wrote that code under employment, i don't have the energy to verify this and that's not my concern, i'm not a lawyer.

But i am mainly interested in whether it is intended to use the "new" license. Because, the messaging is not fully clear. What license is this software supposed to be released under at this point in time? If it is the new license, why does the README say otherwise, despite this repo having commits as recent as this year?