I'm currently rebuilding my implementation JsonSchema.Net from the ground up. I completed 95% of it in a weekend, and it already supports all the published versions Draft 6 and later, including the more complex keywords. Granted, I have a particularly deep understanding of the spec already, but it doesn't feel overly burdensome.
This is intentional because unknown keywords are permitted with JSON Schema 2020-12 and prior. We are changing this with the upcoming version, which means we'll be updating the meta-schema to enforce it as well.
I think the post is generally pretty good. There are some things that I would have stated differently.
"Unfortunately, [the terms] leaked into the documentation that everyone reads"
- We did this on purpose to align everyone's terms. It makes things so much easier when the people asking and answering questions are using the same language.
There are some interesting conceptions of OpenAPI in here as well. Specifically, OpenAPI isn't a JSON Schema document. It's its own kind of document that has JSON Schemas embedded in it.
Still, it's a decent high-level summary. If you're interested in diving a bit deeper, definitely come visit us in Slack (https://json-schema.org/slack).
OpenAPI descriptions are not themselves JSON Schema. They _use_ JSON Schema.
There _are_ JSON Schemas that describe OpenAPI documents as well, but that's just because OpenAPI can be described in JSON.